bluuebunny/crossref_metadata_2025 huggingface dataset:
A Mutation in the POU-Homeodomain of Pit-1 Responsible for Combined Pituitary Hormone Deficiency
Authors: Radovick Sally , Nations Michelle , Du Yuefen , Berg LaVonne A. , Weintraub Bruce D. , Wondisford Fredric E.
Published: October 2006

Pit-1 is a pituitary-specific transcription factor responsible for pituitary development and hormone expression in mammals. Mutations in the gene encoding Pit-1 have been found in two dwarf mouse strains displaying hypoplasia of growth hormone, prolactin, and thyroid-stimulating, hormone-secreting cell types in the anterior pituitary. A point mutation in this gene was identified on one allele in a patient with combined pituitary hormone deficiency. Mutant Pit-1 binds DNA normally but acts as a dominant inhibitor of Pit-1 action in the pituitary.
Production of Syngas by Direct Catalytic Oxidation of Methane
Authors: Hickman D. A. , Schmidt L. D.
Published: October 2006

The reaction between methane and oxygen over platinum and rhodium surfaces in metalcoated ceramic monoliths can be made to produce mostly hydrogen and carbon monoxide (greater than 90% selectivity for both) with almost complete conversion of methane and oxygen at reaction times as short as 10
–3
seconds. This process has great promise for conversion of abundant natural gas into liquid products such as methanol and hydrocarbons, which can be easily transported from remote locations. Rhodium was considerably superior to platinum in producing more H
2
and less H
2
O, which can be explained by the known chemistry and kinetics of reactants, intermediates, and products on these surfaces.
A Cationic Cesium Continuum in Zeolite X
Authors: Sun Tao , Seff Karl , Heo Nam Ho , Petranovskii Vitalii P.
Published: October 2006

A cesium continuum that fills the channels and cavities of zeolite X has been prepared, and its structure has been determined by single-crystal x-ray crystallography. The three-dimensional continuum is cationic to balance the negative charge of the zeolite framework. Its valence electrons, only 0.3 per Cs
+
ion, are widely delocalized over 95 percent of the cesium ions in the crystal. The continuum has a unit cell formula of (Cs
122
)
86+
and contains Cs
13
and Cs
14
clusters (one per supercage) arranged like the atoms in diamond, with one Cs
2
appendix (in the sodalite cavity) per cluster.
Paleozoic Atmospheric CO
2
: Importance of Solar Radiation and Plant Evolution
Authors: Berner Robert A.
Published: October 2006

Changes in solar radiation, as it affects the rate of weathering of silicates on the continents, and other changes involving weathering and the degassing of carbon dioxide (CO
2
) have been included in a long-term carbon-cycle model. These additions to the model show that the major controls on CO
2
concentrations during the Paleozoic era were solar and biological, and not tectonic, in origin. The model predictions agree with independent estimates of a large mid-Paleozoic (400 to 320 million years ago) drop in CO
2
concentrations, which led to large-scale glaciation. This agreement indicates that variations in the atmospheric greenhouse effect were important in global climate change during the distant geologic past.
Protein Catalysis of the Retinal Subpicosecond Photoisomerization in the Primary Process of Bacteriorhodopsin Photosynthesis
Authors: Song Li , El-Sayed M. A. , Lanyi J. K.
Published: October 2006

The rate of retinal photoisomerization in wild-type bacteriorhodopsin (wt bR) is compared with that in a number of mutants in which a positively charged (Arg
82
), a negatively charged (Asp
85
or Asp
212
), or neutral hydrogen bonding (Asp
115
or Tyr
185
) amino acid residue known to be functionally important within the retinal cavity is replaced by a neutral, non-hydrogen bonding one. Only the replacements of the charged residues reduced the photoisomerization rate of the 13-
cis
and
all-trans
isomers present in these mutants by factors of ∼1/4 and ∼1/20, respectively. Retinal photo- and thermal isomerization catalysis and selectivity in wt bR by charged residues is discussed in terms of the known protein structure, the valence-bond wave functions of the ground and excited state of the retinal, and the electrostatic stabilization interactions within the retinal cavity.
Chemistry Community Swarms Into Windy City
Authors: Amato Ivan
Published: October 2006

Two times each year, legions of chemists gather in North America for a massive meeting to discuss the state of the art in their science. The second of this year's get-togethers occurred 2 weeks ago, when the 206th national meeting of the American Chemical Society (ACS) drew about 13,000 chemists, scientists, and onlookers to Chicago. Researchers shared 4800 or so papers and posters on everything from making waste plastic into fuel oil to the chemical basis for the stench of ginkgo fruit to modeling the first instants of photosynthesis.
The Effect of Changing Land Use on Soil Radiocarbon
Authors: Harrison Kevin G. , Broecker Wallace S. , Bonani Georges
Published: October 2006

Most carbon budgets require greening of the terrestrial biosphere as a sink for some of the excess carbon dioxide produced by fossil fuel burning and deforestation. Much of this storage is thought to occur in soils, but running counter to this conclusion is the observation that cultivation has reduced the agricultural reservoir of soil humus. Radiocarbon measurements in agricultural soils lend support to this browning of agricultural lands. Moreover, the loss is from the fast cycling portion of the humus.
Localization of the Pancreatic Beta Cell Glucose Transporter to Specific Plasma Membrane Domains
Authors: Orci Lelio , Thorens Bernard , Ravazzola Mariella , Lodish Harvey F.
Published: October 2006

Immunocytochemical techniques revealed that the "liver-type" glucose transporter is present in the insulin-producing beta cells of rat pancreatic islets but not in other islet endocrine cells. Ultrastructural analysis of the transporter by the protein A-gold technique showed that it is restricted to certain domains of the plasma membrane, its density being sixfold higher in microvilli facing adjacent endocrine cells than in the flat regions of the plasma membrane. These results support a possible role for this glucose transporter in glucose sensing by beta cells and provide evidence that these cells are polarized.
Generation of a Catalytic Antibody by Site-Directed Mutagenesis
Authors: Baldwin Enoch , Schultz Peter G.
Published: October 2006

A hybrid Fv fragment of the dinitrophenyl-binding immunoglobulin A (IgA), MOPC315, has been generated by reconstituting a recombinant variable light chain (V
L
) produced in Escherichia coli with a variable heavy chain (V
H
) derived from the antibody. The Tyr
34
residue of V
L
was substituted by His in order to introduce a catalytic imidazole into the combining site for the ester hydrolysis. The His mutant Fv accelerated the hydrolysis of the 7-hydroxycoumarin ester of 5-(2,4-dinitrophenyl)-aminopentanoic acid 90,000-fold compared to the reaction with 4-methyl imidazole at
p
H 6.8 and had an initial rate that was 45 times as great as that for the wild-type Fv. The hydrolyses of aminopropanoic and aminohexanoic homologs were not significantly accelerated. Thus a single deliberate amino acid change can introduce significant catalytic activity into an antibody-combining site, and chemical modification data can be used to locate potential sites for the introduction of catalytic residues.
A Protein That Binds to a cis-acting Element of Wheat Histone Genes Has a Leucine Zipper Motif
Authors: Tabata Tetsuya , Takase Hisabumi , Takayama Shinobu , Mikami Koji , Nakatsuka Atsunori , Kawata Takefumi , Nakayama Takuya , Iwabuchi Masaki
Published: October 2006

The structure and function of transcription factors of higher plants was studied by isolating cDNA clones encoding a wheat sequence-specific DNA binding protein. A hexameric nucleotide motif, ACGTCA, is located upstream from the TATA box of several plant histone genes. It has been suggested that this motif is essential for efficient transcription of the wheat histone H3 gene. A wheat nuclear protein, HBP-1 (histone DNA binding protein-1), which specifically binds to the hexameric motif, has previously been identified as a putative transcription factor. A cDNA clone encoding HBP-1 has been isolated on the basis of specific binding of HBP-1 to the hexameric motif. The deduced amino acid sequence indicates that HBP-1 contains the leucine zipper motif, which represents a characteristic property of several eukaryotic transcription factors.
Germline Organization of the Murine T Cell Receptor β-Chain Genes
Authors: Chou Hubert S. , Nelson Christopher A. , Godambe Sandip A. , Chaplin David D. , Loh Dennis Y.
Published: October 2006

The complete germline organization of the β-chain genes of the murine T cell receptor was elucidated in order to obtain the structural basis for understanding the mechanisms of somatic DNA rearrangements. Twenty of the 22 known variable (V
β
) genes are clustered within 250 kilobases of DNA 5′ to the constant region (C
β
) genes. These V
β
genes share the same transcriptional orientation as the diversity (D
β
), joining (J
β
), and C
β
genes, which implies that chromosomal deletion is the mechanism for most V
β
to D
β
-J
β
rearrangements. Within this V
β
cluster, the distance between the most proximal V
β
gene and the D
β
-J
β
-C
β
cluster is 320 kilobases, as determined by field-inversion gel electrophoresis. The large distance between V
β
and D
β
, relative to that between D
β
and J
β
, may have significant implications for the ordered rearrangement of the T cell receptor β-chain genes.
Identification of the Human U7 snRNP as One of Several Factors Involved in the 3′ End Maturation of Histone Premessenger RNA's
Authors: Mowry Kimberly L. , Steitz Joan A.
Published: October 2006

In eukaryotic cells, the conversion of gene transcripts into messenger RNA's involves multiple factors, including the highly abundant small nuclear ribonucleoprotein (snRNP) complexes that mediate the splicing reaction. Separable factors are also required for the 3′ end processing of histone pre-mRNA's. The two conserved signals flanking the 3′ cleavage site are recognized by discrete components present in active HeLa cell extracts: the upstream stem loop associates with a nuclease-insensitive factor, while binding to the downstream element is mediated by a component having the properties of a snRNP. The sequence of the RNA moiety of the low abundance human U7 snRNP suggests how the relatively degenerate downstream element of mammalian pre-mRNA's could be recognized by RNA base-pairing.
Translation in Mammalian Cells of a Gene Linked to the Poliovirus 5′ Noncoding Region
Authors: Trono Didier , Pelletier Jerry , Sonenberg Nahum , Baltimore David
Published: October 2006

The central portion (region P) of the 742-nucleotide noncoding 5′ end of poliovirus allows the RNA to initiate protein synthesis in the absence of the usual 5′ 7-methylguanosine capping group. Poliovirus 5′ noncoding region was fused to a reporter gene and transfected into cells. There was extensive augmentation of the expression of this gene by poliovirus-mediated inhibition of cap-dependent protein synthesis. That the construct initiated in a cap-independent manner was verified through in vitro experiments. Small lesions throughout region P blocked its initiation function, implying that a coherent functional unit, hundreds of nucleotides long, is responsible for cap-independent initiation by poliovirus RNA.
A Hydrophobic Transmembrane Segment at the Carboxyl Terminus of thy-1
Authors: Seki Tetsunori , Chang Hsiu-Ching , Moriuchi Tetsuya , Denome Roger , Ploegh Hidde , Silver Jack
Published: October 2006

The mode of integration of the glycoprotein thy-1 within the cell membrane has been controversial due to an apparent lack of a transmembrane hydrophobic segment. Rat and mouse complementary DNA and genomic clones encoding the thy-1 molecule have been isolated and sequenced. These studies have enabled us to determine the intron-exon organization of the thy-1 gene. Furthermore, they have revealed the existence of a sequence which would encode an extra segment (31 amino acids) at the carboxyl terminus of the thy-1 molecule. These extra amino acids include a 20-amino acid hydrophobic segment which may be responsible for integration of thy-1 within the plasma membrane.
Plant Glutamine Synthetase Complements a
glnA
Mutation in
Escherichia coli
Authors: DasSarma Shiladitya , Tischer Edmund , Goodman Howard M.
Published: October 2006

A glutamine synthetase gene from alfalfa (
Medicago sativa
) has been expressed in
Escherichia coli
after fusion of bacterial transcription and translation signals to a complete alfalfa glutamine synthetase coding sequence. Synthesis of the alfalfa glutamine synthetase enzyme in
Escherichia coli
was demonstrated by functional genetic complementation of a glutamine synthetase-deficient mutant and by immunoblotting analysis. These results should facilitate protein engineering and structure-function analysis of the plant enzyme.
Biochemistry of Information Storage in the Nervous System
Authors: Black Ira B. , Adler Joshua E. , Dreyfus Cheryl F. , Friedman Wilma F. , LaGamma Edmund F. , Roach Arthur H.
Published: October 2006

The use of molecular biological approaches has defined new mechanisms that store information in the mammalian nervous system. Environmental stimuli alter steady-state levels of messenger RNA species encoding neurotransmitters, thereby altering synaptic, neuronal, and network function over time. External or internal stimuli alter impulse activity, which alters membrane depolarization and selectively changes the expression of specific transmitter genes. These processes occur in diverse peripheral and central neurons, suggesting that information storage is widespread in the neuraxis. The temporal profile of any particular molecular mnemonic process is determined by specific kinetics of turnover and by the geometry of the neuron resulting in axonal transport of molecules to different synaptic arrays at different times. Generally, transmitters, the agents of millisecond-to-millisecond communication, are subject to relatively long-lasting changes in expression, ensuring that ongoing physiological function is translated into information storage.
ADP-Ribosyltransferase Activity of Pertussis Toxin and Immunomodulation by
Bordetella pertussis
Authors: Black W. J. , Munoz J. J. , Peacock M. G. , Schad P. A. , Cowell J. L. , Burchall J. J. , Lim M. , Kent A. , Steinman L. , Falkow S.
Published: October 2006

Pertussis toxin is produced by the causative agent of whooping cough,
Bordetella pertussis
, and is an adenosine diphosphate (ADP)-ribosyltransferase capable of covalently modifying and thereby inactivating many eukaryotic G proteins involved in cellular metabolism. The toxin is a principal determinant of virulence in whooping cough and is a primary candidate for an acellular pertussis vaccine, yet it is unclear whether the ADP-ribosyltransferase activity is required for both pathogenic and immunoprotective activities. A
B. parapertussis
strain that produced an assembled pertussis holotoxin with only 1 percent of the ADP-ribosyltransferase activity of the native toxin was constructed and was found to be deficient in pathogenic activities associated with
B. parapertussis
including induction of leukocytosis, potentiation of anaphylaxis, and stimulation of histamine sensitivity. Moreover, this mutant strain failed to function as an adjuvant and was less effective in protecting mice from intracerebral challenge infection. These data suggest that the ADP-ribosyltransferase activity is necessary for both pathogenicity and optimum immunoprotection. These findings bear directly on the design of a nontoxic pertussis vaccine.
The Involvement of Platelet Activating Factor in Ovulation
Authors: Abisogun Akinwunmi O. , Braquet Pierre , Tsafriri Alex
Published: October 2006

Follicle rupture during ovulation is associated with inflammation-like changes. Because platelet activating factor (PAF) participates in the inflammatory process, the effect of a PAF-specific antagonist, BN52021, on the ovulatory response was tested in rats. BN52021, administered locally, inhibited follicle rupture in rats stimulated to ovulate with human chorionic gonadotropin (hCG). In addition to suppressing rupture of the follicles, this antagonist suppressed the hCG-stimulated increase in ovarian collagenolysis and vascular permeability. The inhibition of ovulation of BN52021 could be reversed by simultaneous administration of PAF. Furthermore, PAF partially reversed the blockage of ovulation by inhibitors of eicosanoid synthesis. Collectively, these results suggest the involvement of PAF in ovulation. Its role seems to be closely related to the metabolism of arachidonic acid. Thus, modulation of PAF action may serve as an additional target for regulation of reproduction via its action on ovulation.
Structurally Divergent Human T Cell Receptor γ Proteins Encoded by Distinct Cγ Genes
Authors: Krangel Michael S. , Band Hamid , Hata Shingo , McLean Joanne , Brenner Michael B.
Published: October 2006

The human T cell receptor (TCR) γ polypeptide occurs in structurally distinct forms on certain peripheral blood T lymphocytes. Complementary DNA clones representing the transcripts of functionally rearranged TCR γ genes in these cells have been analyzed. The expression of a disulfide-linked and a nondisulfide-linked form of TCR γ correlates with the use of the Cγ1 and Cγ2 constant-region gene segments, respectively. Variability in TCR γ polypeptide size and disulfide linkage is determined by the number of copies and the sequence of a repeated segment of the constant region. Thus, Cγ1 and Cγ2 are used to generate structurally distinct, yet functional, T3-associated receptor complexes on peripheral blood lymphocytes. Tryptic peptide mapping suggests that the T3-associated TCR γ and δ peptides in the nondisulfide-linked form are distinct.
Molecular Crowding on the Cell Surface
Authors: Ryan T. A. , Myers J. , Holowka D. , Baird B. , Webb W. W.
Published: October 2006

Strong steric interactions among proteins on crowded living cell surfaces were revealed by measurements of the equilibrium spatial distributions of proteins in applied potential gradients. The fraction of accessible surface occupied by mobile surface proteins can be accurately represented by including steric exclusion in the statistical thermodynamic analysis of the data. The analyses revealed enhanced, concentration-dependent activity coefficients, implying unanticipated thermodynamic activity even at typical cell surface receptor concentrations.
A Transcriptional Enhancer 3′ of C
β2
in the T Cell Receptor β Locus
Authors: McDougall Skye , Peterson Craig L. , Calame Kathryn
Published: October 2006

Run-on transcription experiments were used to demonstrate that transcription of T cell receptor β chain V genes is activated by DNA rearrangement, in a manner similar to immunoglobulin genes. A transcriptional enhancer likely to be involved in this activation has been identified. A 25-kilobase region from J
β1
to V
β14
was tested for enhancer activity by transient transfections, and an enhancer was found 7.5 kilobases 3′ of C
β2
. The β enhancer has low activity relative to the simian virus 40 viral enhancer, does not display a preference for V
β
promoters, has a T cell-specific activity, and binds two purified immunoglobulin heavy chain enhancer factors.
Selection of Variable-Joining Region Combinations in the α Chain of the T Cell Receptor
Authors: Roth Matthew E. , Lacy Michael J. , McNeil Leslie Klis , Kranz David M.
Published: October 2006

Most T lymphocytes express an antigen-specific receptor composed of two subunits, α and β, each of which can exhibit structural variability. A complex selection process operates on T cells during development in the thymus such that cells expressing only particular αβ-receptors migrate to the periphery. The α -chain repertoire was dissected at different stages of the selection process by using the polymerase chain reaction (PCR) technique to amplify only those transcripts of a particular variable region gene (V
58
). Sequences from these V
58
cDNAs reveal the predominant expression of four joining (J) segments by T cells in the adult thymus, suggesting that molecular or cellular processes select particular V
α
J
α
combinations during development. T cells expressing one of these V
58
J
α
chains appear to have been negatively selected at a later stage, since these transcripts were present in the spleen at approximately one-tenth the level in the thymus. Results also indicate that residues present at the V
α
J
α
junction may be important in an early selection process.
Microinjected DNA from the X Chromosome Affects Sex Determination in
Caenorhabditis elegans
Authors: McCoubrey William K. , Nordstrom Kim D. , Meneely Philip M.
Published: October 2006

The signal for sex determination in the nematode
Caenorhabditis elegans
is the ratio of the number of X chromosomes to the number of sets of autosomes (X/A ratio). By previous genetic tests, elements that feminized chromosomal males appeared to be widespread on the X chromosome, but the nature of these elements was not determined. In experiments to define a feminizing element molecularly, cloned sequences were added to chromosomally male embryos by microinjection into the mother. Three different X-chromosome clones, including part of an actin gene, part of a myosin heavy chain gene, and all of two myosin light chain genes, feminize chromosomal males. Both somatic and germline aspects of sex determination are affected. In contrast, about 40 kilobases of nematode autosomal DNA, phage lambda DNA, and plasmid pBR322 DNA do not affect sex determination. A feminizing region was localized to a maximum of 131 base pairs within an intron of the X-linked actin gene; a part of the gene that does not have this region is not feminizing. The results suggest that short, discrete elements found associated with many X-linked genes may act as signals for sex determination in
C. elegans
.
Morphine-Induced Delay of Normal Cell Death in the Avian Ciliary Ganglion
Authors: Meriney Stephen D. , Gray D. Bruce , Pilar Guillermo
Published: October 2006

Repeated administration of morphine in increasing doses delayed normal cell death in the ciliary ganglion of the chick embryo; the effect was completely blocked by naloxone. Survival of spinal motoneurons was not affected. Morphine also inhibited potassium-stimulated synthesis of acetylcholine in ganglion cells cocultured with muscle, suggesting that morphine can influence neurotransmission. Morphine's effect on cell death may be due to an inhibition of transmission at the neuromuscular junction, but opiates may also directly affect cell death. Although it is not known whether the endogenous opiates in the ciliary ganglion influence neuronal survival during embryogenesis, exogenous opiates can affect normal cell death in the autonomic nervous system.
Promoter Region of the Human Harvey
ras
Proto-Oncogene: Similarity to the EGF Receptor Proto-Oncogene Promoter
Authors: Ishii Shunsuke , Merlino Glenn T. , Pastan Ira
Published: October 2006

Regulation of transcription of members of the
ras
gene family undoubtably plays an important role in controlling cellular growth. Examination of this level of regulation requires identification of the promoter regions of the
ras
proto-oncogenes. Four major transcriptional start sites were detected in the human Harvey
ras
1 proto-oncogene. The promoter region contains neither a TATA box nor a CAAT box in their characteristic upstream positions, has an extremely high G+C content (80 percent), and contains multiple GC boxes including seven CCGCCC repeats and three repeats of the inverted complement, GGGCGG. This region has strong promoter activity when placed upstream from the chloramphenicol acetyl transferase gene and transfected into monkey CV1 cells. In these ways the Harvey
ras
1 proto-oncogene promoter resembles the promoter of the gene encoding the epidermal growth factor (EGF) receptor. The similarity between the two proto-oncogene promoters may be relevant to the mechanism by which the expression of such "growth control" genes is regulated.
Expression Cloning of a Lymphocyte Homing Receptor cDNA: Ubiquitin Is the Reactive Species
Authors: St John Tom , Gallatin W. Michael , Siegelman Mark , Smith Harry T. , Fried Victor A. , Weissman Irving L.
Published: October 2006

The lymphocyte cell surface receptor for the high endothelial venules (HEV's) of peripheral lymph nodes is specifically recognized by the monoclonal antibody MEL-14. Three independent complementary DNA (cDNA) clones, each of which encodes the protein ubiquitin, were detected by virtue of the expression of the MEL-14 antigenic determinant on cDNA-β-galactosidase bacterial fusion proteins. The antigenic determinant defined by MEL-14 resides in the carboxyl terminal 13-amino-acid proteolytic peptide of ubiquitin, but is undetected in intact undenatured ubiquitin and other cellular ubiquitinated proteins. Antisera and monoclonal antibodies to ubiquitin determinants bind to the surface of both HEV-receptor positive and negative cell lines. The MEL-14-identified cDNA clones hydridize to RNA transcripts that encode tandemly repeated ubiquitins. Sequence analysis of these polyubiquitin cDNA's does not identify a leader sequence for export to the cell surface. The expression of the MEL-14 epitope of ubiquitin depends upon its local environment. The steady-state levels of expression of the ubiquitin messenger RNA's do not correlate with either the tissue derivation of the RNA or the expression of the lymphocyte HEV receptor. Regulation of the expression of the HEV receptor is not likely to reflect the transcriptional control of ubiquitin genes, but rather to reflect control of the expression of the HEV core polypeptide or its level or form of ubiquitination.
Two Elements in the Bovine Leukemia Virus Long Terminal Repeat That Regulate Gene Expression
Authors: Derse David , Casey James W.
Published: October 2006

The bovine leukemia virus, like the human T-cell leukemia viruses (HTLV-I and HTLV-II), are unusual biologically in that viral transcripts are not detected in tumors or infected tissues. The bovine leukemia virus long terminal repeat (BLV LTR) functions as a transcriptional promoter only in cell lines productively infected with BLV. Deletion mapping indicated that at least two regions of the LTR, on the 5′ and 3′ sides of the RNA start site, influenced gene expression. An analysis has now been made of the effects of coupling sequences from these LTR regions to a heterologous core promoter derived from the SV40 early promoter unit. Through the use of the transient expression of the bacterial chloramphenicol acetyltransferase (CAT) gene to monitor transcriptional activity in vivo, two independent, regulatory elements were identified in the BLV LTR. One was present in a fragment of 75 base pairs derived from the U3 region of the LTR and behaved much like other enhancer elements. It may be a major determinant of BLV expression in productively infected cell lines, since it enhanced transcription controlled by the heterologous core promoter only in these cells. The second element was contained in a 250-bp fragment derived from LTR sequences in the R region, located downstream from the RNA start site. Its activation of CAT expression was not dependent on BLV infection and was evident only when the fragment was located immediately downstream from the RNA start site. BLV expression thus appears to be regulated in part by a cell-specific enhancer element upstream from the core promoter and a novel sequence downstream from the RNA initiation site in the viral LTR.
Trans
-Activator Gene of HTLV-II Induces IL-2 Receptor and IL-2 Cellular Gene Expression
Authors: Greene Warner C. , Leonard Warren J. , Wano Yuji , Svetlik Penny B. , Peffer Nancy J. , Sodroski Joseph G. , Rosen Craig A. , Goh Wei Chun , Haseltine William A.
Published: October 2006

The human T-lymphotropic viruses types I and II (HTLV-I and -II) have been etiologically linked with certain T-cell leukemias and lymphomas that characteristically display membrane receptors for interleukin-2. The relation of these viruses to this growth factor receptor has remained unexplained. It is demonstrated here that introduction of the
trans
-activator (
tat
) gene of HTLV-II into the Jurkat T-lymphoid cell line results in the induction of both interleukin-2 receptor and interleukin-2 gene expression. The coexpression of these cellular genes may play a role in the altering T-cell growth following retroviral infection.
Return of Myosin Heads to Thick Filaments After Muscle Contraction
Authors: Yagi N. , Ito M. H. , Nakajima H. , Izumi T. , Matsubara I.
Published: October 2006

The heads of myosin molecules, which move to the vicinity of the thin filaments to react with actin during muscle contraction, return to the thick filaments after contraction. The return occurs in two stages; a rapid return of the majority of the myosin heads is followed by a slow return of the rest.
Neuroleukin: A Lymphokine Product of Lectin-Stimulated T Cells
Authors: Gurney Mark E. , Apatoff Brian R. , Spear Gregory T. , Baumel Mark J. , Antel Jack P. , Bania Margaret Brown , Reder Anthony T.
Published: October 2006

Neuroleukin is a lymphokine product of lectin-stimulated T cells that induces immunoglobulin secretion by cultured human peripheral blood mononuclear cells. Neuroleukin acts early in the in vitro response that leads to formation of antibody-secreting cells, but continued production of immunoglobulin by differentiated antibody-secreting cells is neuroleukin-independent. Although the factor is not directly mitogenic, cellular proliferation is a late component of the response to neuroleukin. Neuroleukin does not have B-cell growth factor (BCGF) or B-cell differentiation factor (BCDF) activity in defined assays. Neuroleukin-evoked induction of immunoglobulin secretion is both monocyte- and T cell-dependent.
Structure of the DNA-Eco RI Endonuclease Recognition Complex at 3 Å Resolution
Authors: McClarin Judith A. , Frederick Christin A. , Wang Bi-Cheng , Greene Patricia , Boyer Herbert W. , Grable John , Rosenberg John M.
Published: October 2006

The crystal structure of the complex between Eco RI endonuclease and the cognate oligonucleotide TCGCGAATTCGCG provides a detailed example of the structural basis of sequence-specific DNA-protein interactions. The structure was determined, to 3 Å resolution, by the ISIR (iterative single isomorphous replacement) method with a platinum isomorphous derivative. The complex has twofold symmetry. Each subunit of the endonuclease is organized into an α/β domain consisting a five-stranded β sheet, α helices, and an extension, called the "arm," which wraps around the DNA. The large β sheet consists of antiparallel and parallel motifs that form the foundations for the loops and α helices responsible for DNA strand scission and sequence-specific recognition, respectively. The DNA cleavage site is located in a cleft that binds the DNA backbone in the vicinity of the scissile bond. Sequence specificity is mediated by 12 hydrogen bonds originating from α helical recognition modules. Arg
200
forms two hydrogen bonds with guanine while Glu
144
and Arg
145
form four hydrogen bonds to adjacent adenine residues. These interactions discriminate the Eco RI hexanucleotide GAATTC from all other hexanucleotides because any base substitution would require rupture of at least one of these hydrogen bonds.
The Atomic Structure of Mengo Virus at 3.0 Å Resolution
Authors: Luo Ming , Vriend Gerrit , Kamer Greg , Minor Iwona , Arnold Edward , Rossmann Michael G. , Boege Ulrike , Scraba Douglas G. , Duke Greg M. , Palmenberg Ann C.
Published: October 2006

The structure of Mengo virus, a representative member of the cardio picornaviruses, is substantially different from the structures of rhino- and polioviruses. The structure of Mengo virus was solved with the use of human rhinovirus 14 as an 8 Å resolution structural approximation. Phase information was then extended to 3 Å resolution by use of the icosahedral symmetry. This procedure gives promise that many other virus structures also can be determined without the use of the isomorphous replacement technique. Although the organization of the major capsid proteins VP1, VP2, and VP3 of Mengo virus is essentially the same as in rhino- and polioviruses, large insertions and deletions, mostly in VP1, radically alter the surface features. In particular, the putative receptor binding "canyon" of human rhinovirus 14 becomes a deep "pit" in Mengo virus because of polypeptide insertions in VP1 that fill part of the canyon. The minor capsid peptide, VP4, is completely internal in Mengo virus, but its association with the other capsid proteins is substantially different from that in rhino- or poliovirus. However, its carboxyl terminus is located at a position similar to that in human rhinovirus 14 and poliovirus, suggesting the same autocatalytic cleavage of VP0 to VP4 and VP2 takes place during assembly in all these picornaviruses.
U3 Sequences from HTLV-I and -II LTRs Confer p
x
Protein Response to a Murine Leukemia Virus LTR
Authors: Kitado Haruo , Chen Irvin S.-Y. , Shah Neil P. , Cann Alan J. , Shimotohno Kunitada , Fan Hung
Published: October 2006

Human T-cell leukemia virus (HTLV) types I and II are unusual among replication-competent retroviruses in that they contain a fourth gene (
x
) necessary for replication. The
x
gene product, p
x
, transcriptionally transactivates the viral long terminal repeat (LTR), and is thus a positive regulator. To investigate p
x
transactivation, sequences from the U3 regions of the LTRs of HTLV-I and -II were inserted into the Moloney murine leukemia virus (M-MuLV) LTR by recombinant DNA techniques. Transient expression assays of the chimeric LTRs indicated that the HTLV sequences conferred to the M-MuLV LTR responsiveness to HTLV p
x
protein. M-MuLV enhancers were not required for function of the chimeric LTRs. Infectious recombinant M-MuLVs containing chimeric LTRs were also generated. These viruses showed higher infectivity when assayed in mouse cells expressing HTLV-II p
x
protein compared to normal mouse cells. Thus the HTLV sequences were able to confer p
x
responsiveness to infectious M-MuLV. The generation of a virus dependent on a transactivating protein for its replication has implications for the evolution of the human T-cell leukemia viruses.
Expression of the art/trs Protein of HIV and Study of Its Role in Viral Envelope Synthesis
Authors: Knight David M. , Flomerfelt Francis A. , Ghrayeb John
Published: October 2006

The art/trs transactivator protein of human immunodeficiency virus (HIV) was expressed in mammalian cells as a 19-kilodalton protein that was immunoreactive with sera from HIV-infected patients. Separate plasmids encoding the art/trs protein, the tat protein, or the envelope glycoprotein gp120 were used to demonstrate that both art/trs and tat are absolutely required for the synthesis of gp120 from its cognate messenger RNA. In addition, both the tat and art/trs proteins influence the level of envelope RNA. The results suggest that art/trs and tat may be ideal targets for potential anti-HIV agents in AIDS therapy.
Switch in Immunoglobulin Class Production Observed in Single Clones of Committed Lymphocytes
Authors: Wabl Matthias R. , Forni Luciana , Loor Francis
Published: October 2006

Mouse spleen cells, after stimulation with lipopolysaccharide, were cloned in culture. After 4 to 5 days, the daughter cells were stained and examined for immunoglobulin class with double immunofluorescent reagents. A switch of the stained color of these cells was observed, implying a switch from imunoglobulin M to immunoglobulin G production in the progeny of a single B cell.
Regulation of Expression of the Interleukin-2 Receptor on Hematopoietic Cells by Interleukin-3
Authors: Birchenall-Sparks Maria C. , Farrar William L. , Rennick Donna , Kilian Patricia L. , Ruscetti Francis W.
Published: October 2006

Remarkable similarities in the intracellular and genetic events occur when lymphoid and hematopoietic cells are exposed to their specific growth factors. The interleukin-2 (IL-2) receptor, whose cell-surface expression is an absolute requirement for the growth and differentiation of lymphoid cells, was detected on various nonlymphoid hematopoietic cell types in this study. Cell lines consisting either of granulocyte-macrophage precursors or mast cells, which are dependent on interleukin-3 (IL-3) for their growth, expressed high levels of the IL-2 receptor on their surface. Analysis of the binding characteristics of these receptors with
125
I-labeled recombinant IL-2 revealed that only receptors with low affinity for IL-2 were present on these cells. Addition of purified recombinant IL-3 to these cell lines led to an increase in IL-2 receptor gene expression within 1 hour in isolated nuclei. This IL-3-induced increase in the number of IL-2 receptors on the cell surface is maximal within 24 hours. Addition of 10,000 units of IL-2 to these cells had no apparent effect on their growth or differentiation. The presence of the receptor with only low affinity for IL-2 on hematopoietic cells and the regulation by IL-3 suggest that this receptor is involved in some important metabolic event in hematopoiesis.
A Synaptic Vesicle Protein with a Novel Cytoplasmic Domain and Four Transmembrane Regions
Authors: Südhof Thomas C. , Lottspeich Friedrich , Greengard Paul , Mehl Ehrenfried , Jahn Reinhard
Published: October 2006

Complementary DNA and genomic clones were isolated and sequenced corresponding to rat and human synaptophysin (p38), a major integral membrane protein of synaptic vesicles. The deduced amino acid sequences indicate an evolutionarily highly conserved protein that spans the membrane four times. Both amino and carboxyl termini face the cytoplasm, with the latter containing ten copies of a tyrosine-rich pentapeptide repeat. The structure of synaptophysin suggests that the protein may function as a channel in the synaptic vesicle membrane, with the carboxyl terminus serving as a binding site for cellular factors.
Regulation of Gene Expression by Interferons: Control of H-2 Promoter Responses
Authors: Korber Bette , Mermod Nicolas , Hood Leroy , Stroynowski Iwona
Published: October 2006

The magnitude of the response to interferons and the requirement for individual elements in the promoter of the H-2D
d
gene were shown to be cell-specific and dependent on the type of interferon used. Three DNA sequences in the promoter were found to bind murine nuclear factors. Two of these sequences are in functionally defined enhancer regions and also bind to the transcription factor AP-1. The third sequence is part of the region involved in interferon regulation and is homologous to the enhancer element of the interferon β gene. A model for interferon regulation of H-2 promoters is discussed.
Induction of the Intermediate Pituitary by Stress: Synthesis and Release of a Nonopioid Form of β-Endorphin
Authors: Akil Huda , Shiomi Hirohito , Matthews John
Published: October 2006

β-Endorphin in the intermediate lobe of the pituitary gland is posttranslationally modified to produce opioid inactive peptides. Whether these are metabolites or biologically relevant products has not been known. It was found that repeated stress induces increased biosynthesis and release of β-endorphin-like substances from the intermediate lobe of rats and that opioid-inactive
N
-acetylated β-endorphin-(1-31) is selectively made and liberated. The possible role of this nonopioid product and the selective release of peptide forms are discussed.
Constraint of the Translational Diffusion of a Membrane Glycoprotein by Its External Domains
Authors: Wier Marjorie , Edidin Michael
Published: October 2006

The translational diffusion of wild-type and underglycosylated molecules of a membrane-integral glycoprotein the L
d
class I major histocompatibility complex (MHC) antigen has been measured. The L
d
mutant molecules, which lack one or more glycosylation sites, had larger translational diffusion coefficients,
D
, than did wild-type L
d
molecules glycosylated at three sites. The increase in
D
is linear with loss of glycosylation. The highest value of
D
approaches that for translational diffusion of molecules constrained only by viscosity of the membrane lipid bilayer. These results indicate that the external portions of cell surface glycoproteins interact significantly with other nearby molecules.
Recognition of a DNA Operator by the Repressor of Phage 434: A View at High Resolution
Authors: Aggarwal Aneel K. , Rodgers David W. , Drottar Marie , Ptashne Mark , Harrison Stephen C.
Published: October 2006

The repressors of temperate bacteriophages such as 434 and lambda control transcription by binding to a set of DNA operator sites. The different affinity of repressor for each of these sites ensures efficient regulation. High-resolution x-ray crystallography was used to study the DNA-binding domain of phage 434 repressor in complex with a synthetic DNA operator. The structure shows recognition of the operator by direct interactions with base pairs in the major groove, combined with the sequence-dependent ability of DNA to adopt the required conformation on binding repressor. In particular, a network of three-centered bifurcated hydrogen bonds among base pairs in the operator helps explain why 434 repressor prefers certain sites over others. These bonds, which stabilize the conformation of the bound DNA, can form only with certain sequences.
Gene Cloning and Containment Properties of Plasmid Col E1 and Its Derivatives
Authors: Armstrong Karen A. , Hershfield Vickers , Helinski Donald R.
Published: October 2006

Colicinogenic plasmid E1 (Col E1) and Col E1 derivatives offer advantages as plasmid cloning vehicles with regard to both utility and biological containment. The Col E1 derivative pCR1 does not alter those essential characteristics of the enfeebled
Escherichia coli
strain χ1776 that make this strain particularly useful as a host-vehicle system for recombinant DNA research.
Increase in Conjugational Transmission Frequency of Nonconjugative Plasmids
Authors: Crisona Nancy J. , Clark Alvin J.
Published: October 2006

Addition of Eco RI fragment 6 of the
Escherichia coli
sex factor F to pSC101 increases the frequency of its transmission by RI-19 and ColVB. Transmission frequencies of pSC101 and two pSC101 chimeras are also increased after the putative transposition of drug resistance element Tn3 from RI-19. These increases may result from addition of an origin of conjugational transfer to the plasmids.
Degradation of DNA by Nucleases in Intestinal Tract of Rats
Authors: Maturin Larry , Curtiss Roy
Published: October 2006

Strains of
Escherichia coli
K12 have been constructed as safer hosts for use in recombinant DNA research, These strains are unable to survive passage through the intestinal tracts of rats because of a constellation of mutations conferring bile sensitivity and requirements for diaminopimelic acid and thymine. Since death caused by diaminopimelic acid deprivation could release recombinant DNA before DNA is degraded because of thymine starvation, it is important to determine the "survival potential" of the released DNA's. Bacterial and plasmid DNA's extracted from bacterial cells are rapidly degraded when added to low dilutions of rat intestinal contents. This observation, coupled with the stringent requirements necessary for in vitro transformation or transfection, make in vivo transmission of naked recombinant DNA in the rat intestinal tract highly improbable.
Performance Assessment of Radioactive Waste Repositories
Authors: Campbell James E. , Cranwell Robert M.
Published: October 2006

The current plans for permanent disposal of radioactive waste call for its emplacement in deep underground repositories mined from geologically stable rock formations. The U.S. Nuclear Regulatory Commission and U.S. Environmental Protection Agency have established regulations setting repository performance standards for periods of up to 10,000 years after disposal. Compliance with these regulations will be based on a performance assessment that includes (i) identification and evaluation of the likelihood of all significant processes and events that could affect a repository, (ii) examination of the effects of these processes and events on the performance of a repository, and (iii) estimation of the releases of radionuclides, including the associated uncertainties, caused by these processes and events. These estimates are incorporated into a probability distribution function showing the likelihood of exceeding radionuclide release limits specified by regulations.
Independent Molecular Pathways in Initiation and Loss of Hormone Responsiveness of Breast Carcinomas
Authors: Sukumar Saraswati , Carney Walter P. , Barbacid Mariano
Published: October 2006

These studies were set up to determine whether those oncogenes participating in the initiation of mammary carcinogenesis (for example,
ras
oncogenes) play a direct role in the outcome of events associated with the late stages of tumor development such as loss of hormone dependency. Mammary carcinomas induced by a single carcinogenic insult in pubescent rats was selected as an in vivo model system with direct relevance to human breast cancer. Acquisition of hormone-independent growth in these carcinogen-induced tumors was found to be independent of the activation of
ras
oncogenes during the early stages of carcinogenesis. In agreement with these observations, introduction of a human
ras
oncogene into human MCF-7 breast carcinoma cells did not abrogate their hormonal dependency for growth in vivo. These findings suggest that those events responsible for the critical stages of breast cancer development occur independently and in an uncoordinated manner.
H-Y Antigen and the Genetics of Sex Determination
Authors: Wachtel Stephen S.
Published: October 2006

Widespread phylogenetic conservation of H-Y antigen indicates persistence of a vital function. It has been proposed that this function is the primary determination of mammalian sex. According to this proposal, the indifferent embryonic gonad is induced to differentiate as a testis in the presence of H-Y antigen, and as an ovary in the absence of H-Y antigen. But presence of H-Y antigen does not guarantee testicular differentiation. Other factors may be required: a gene that activates the H-Y structural locus, and another gene that codes for specific H-Y antigen receptors.
Direct Observation of the Femtosecond Excited-State
cis
-
trans
Isomerization in Bacteriorhodopsin
Authors: Mathies Richard A. , Brito Cruz C. H. , Pollard Walter T. , Shank Charles V.
Published: October 2006

Femtosecond optical measurement techniques have been used to study the primary photoprocesses in the light-driven transmembrane proton pump bacteriorhodopsin. Light-adapted bacteriorhodopsin was excited with a 60-femtosecond pump pulse at 618 nanometers, and the transient absorption spectra from 560 to 710 nanometers were recorded from -50 to 1000 femtoseconds by means of 6-femtosecond probe pulses. By 60 femtoseconds, a broad transient hole appeared in the absorption spectrum whose amplitude remained constant for about 200 femtoseconds. Stimulated emission in the 660- to 710-nanometer region and excited-state absorption in the 560- to 580-nanometer region appeared promptly and then shifted and decayed from 0 to ∼150 femtoseconds. These spectral features provide a direct observation of the 13-
trans
to 13-
cis
torsional isomerization of the retinal chromophore on the excited-state potential surface. Absorption due to the primary ground-state photoproduct J appears with a time constant of ∼500 femtoseconds.
Long Lives for Homozygous Trembler Mutant Mice Despite Virtual Absence of Peripheral Nerve Myelin
Authors: Henry Earl Webb , Sidman Richard L.
Published: October 2006

Nervous system functions are dependent on point-to-point communication of signals along neuronal axons, and axonal insulation by myelin is thought to speed such conduction. Loss of previously formed myelin or lack of myelin formation can have serious, even fatal, consequences. Mice homozygous for the trembler mutation make virtually no peripheral nervous system myelin, yet have long and functional lives. This result calls into question the view that peripheral nervous system myelin plays a vital role, at least in this species.