bluuebunny/crossref_metadata_2025 huggingface dataset:
Signaling the Arrest of Pollen Tube Development in Self-Incompatible Plants
Authors: Nasrallah J. B. , Stein J. C. , Kandasamy M. K. , Nasrallah M. E.
Published: October 2006

Self-incompatibility (SI), the cellular recognition system that limits inbreeding, has served as a paradigm for the study of cell-to-cell communication in plants since the phenomenon was first described by Darwin. Recent studies indicate that SI is achieved by diverse molecular mechanisms in different plant species. In the mustard family, the mechanism of SI shows parallels to the signaling systems found in animals that are mediated by cell-surface receptors with signal-transducing protein kinase activity.
Physicists Find Windows of Opportunity in Plasmas
Authors: Glanz James
Published: October 2006

The 1500 physicists from Europe, the United States, the Pacific Rim, and the former Soviet Union who gathered in Minneapolis from 7 to 11 November had many messages but one medium: plasmas. As the presentations at the meeting of the American Physical Society's division of plasma physics showed, the windows that laboratory plasmas can provide into space, turbulent liquids, and matter-antimatter interactions are opening wider than ever.
In Situ Determination of the NiAs Phase of FeO at High Pressure and Temperature
Authors: Fei Yingwei , Mao Ho-kwang
Published: October 2006

In situ synchrotron x-ray diffraction measurements of FeO at high pressures and high temperatures revealed that the high-pressure phase of FeO has the NiAs structure (B8). The lattice parameters of this NiAs phase at 96 gigapascals and 800 kelvin are
a
= 2.574(2) angstroms and
c
= 5.172(4) angstroms (the number in parentheses is the error in the last digit). Metallic behavior of the high-pressure phase is consistent with a covalently and metallically bonded NiAs structure of FeO. Transition to the NiAs structure of FeO would enhance oxygen solubility in molten iron. This transition thus provides a physiochemical basis for the incorporation of oxygen into the Earth's core.
The Accumulation Record from the GISP2 Core as an Indicator of Climate Change Throughout the Holocene
Authors: Meese D. A. , Gow A. J. , Grootes P. , Stuiver M. , Mayewski P. A. , Zielinski G. A. , Ram M. , Taylor K. C. , Waddington E. D.
Published: October 2006

A depth-age scale and an accumulation history for the Holocene have been established on the Greenland Ice Sheet Project 2 (GISP2) deep core, providing the most continuously dated record of annual layer accumulation currently available. The depth-age scale was obtained with the use of various independent techniques to count annual layers in the core. An annual record of surface accumulation during the Holocene was obtained by correcting the observed layer thicknesses for flow-thinning. Fluctuations in accumulation provide a continuous and detailed record of climate variability over central Greenland during the Holocene. Climate events, including "Little Ice Age" type events, are examined.
The Clementine Mission to the Moon: Scientific Overview
Authors: Nozette Stewart , Rustan P. , Pleasance L. P. , Kordas J. F. , Lewis I. T. , Park H. S. , Priest R. E. , Horan D. M. , Regeon P. , Lichtenberg C. L. , Shoemaker E. M. , Eliason E. M. , McEwen A. S. , Robinson M. S. , Spudis P. D. , Acton C. H. , Buratti B. J. , Duxbury T. C. , Baker D. N. , Jakosky B. M. , Blamont J. E. , Corson M. P. , Resnick J. H. , Rollins C. J. , Davies M. E. , Lucey P. G. , Malaret E. , Massie M. A. , Pieters C. M. , Reisse R. A. , Smith D. E. , Sorenson T. C. , Breugge R. W. Vorder , Zuber M. T.
Published: October 2006

In the course of 71 days in lunar orbit, from 19 February to 3 May 1994, the Clementine spacecraft acquired just under two million digital images of the moon at visible and infrared wavelengths. These data are enabling the global mapping of the rock types of the lunar crust and the first detailed investigation of the geology of the lunar polar regions and the lunar far side. In addition, laser-ranging measurements provided the first view of the global topographic figure of the moon. The topography of many ancient impact basins has been measured, and a global map of the thickness of the lunar crust has been derived from the topography and gravity.
The Shape and Internal Structure of the Moon from the Clementine Mission
Authors: Zuber Maria T. , Smith David E. , Lemoine Frank G. , Neumann Gregory A.
Published: October 2006

Global topographic and gravitational field models derived from data collected by the Clementine spacecraft reveal a new picture of the shape and internal structure of the moon. The moon exhibits a 16-kilometer range of elevation, with the greatest topographic excursions occurring on the far side. Lunar highlands are in a state of near-isostatic compensation, whereas impact basins display a wide range of compensation states that do not correlate simply with basin size or age. A global crustal thickness map reveals crustal thinning under all resolvable lunar basins. The results indicate that the structure and thermal history of the moon are more complex than was previously believed.
Ancient Multiring Basins on the Moon Revealed by Clementine Laser Altimetry
Authors: Spudis Paul D. , Gillis Jeffrey J. , Reisse Robert A.
Published: October 2006

Analysis of laser altimetry data from Clementine has confirmed and extended our knowledge of nearly obliterated multiring basins on the moon. These basins were formed during the early bombardment phase of lunar history, have been filled to varying degrees by mare lavas and regional ejecta blankets, and have been degraded by the superposition of large impact craters. The Mendel-Rydberg Basin, a degraded three-ring feature over 600 kilometers in diameter on the lunar western limb, is about 6 kilometers deep from rim to floor, only slightly less deep than the nearby younger and much better preserved Orientale Basin (8 kilometers deep). The South Pole—Aitken Basin, the oldest discernible impact feature on the moon, is revealed as a basin 2500 kilometers in diameter with an average depth of more than 13 kilometers, rim crest to floor. This feature is the largest, deepest impact crater yet discovered in the solar system. Several additional depressions seen in the data may represent previously unmapped ancient impact basins.
Nanomaterials: A Membrane-Based Synthetic Approach
Authors: Martin Charles R.
Published: October 2006

Materials with nanoscopic dimensions not only have potential technological applications in areas such as device technology and drug delivery but also are of fundamental interest in that the properties of a material can change in this regime of transition between the bulk and molecular scales. In this article, a relatively new method for preparing nanomaterials, membrane-based synthesis, is reviewed. This method entails synthesis of the desired material within the pores of a nanoporous membrane. Because the membranes used contain cylindrical pores of uniform diameter, monodisperse nanocylinders of the desired material, whose dimensions can be carefully controlled, are obtained. This "template" method has been used to prepare polymers, metals, semiconductors, and other materials on a nanoscopic scale.
Isotopic Composition of Old Ground Water from Lake Agassiz: Implications for Late Pleistocene Climate
Authors: Remenda V. H. , Cherry J. A. , Edwards T. W. D.
Published: October 2006

A uniform oxygen isotope value of –25 per mil was obtained from old ground water at depths of 20 to 30 meters in a thick deposit of clay in the southern part of the glacial Lake Agassiz basin. The lake occupied parts of North Dakota and southern Manitoba at the end of the last glacial maximum and received water from the ice margin and the interior plains region of Canada. Ground water from thick late Pleistocene-age clay deposits elsewhere, a till in southern Saskatchewan, and a glaciolacustrine deposit in northern Ontario show the same value at similar depths. These sites are at about 50°N latitude, span a distance of 2000 kilometers, and like the Lake Agassiz sites, have a ground-water velocity of less than a few millimeters per year. The value of –25 per mil is characteristic of meltwater impounded in the southern basin of Lake Agassiz. This value corresponds to an estimated air temperature of –16°C, compared with the modern temperature of 0°C for this area.
Trans-Acting Dosage Effects on the Expression of Model Gene Systems in Maize Aneuploids
Authors: Guo Mei , Birchler James A.
Published: October 2006

The reduction in vigor of aneuploids was classically thought to be due to the imbalance of gene products expressed from the varied chromosome relative to those from the remainder of the genome. In this study, the dosage of chromosomal segments was varied, but the transcript level of most genes encoded therein showed compensation for the number of copies of the gene. Genes whose dosage was not altered were affected by aneuploidy of unlinked chromosomal segments. The phenotypic effects of aneuploidy and of a substantial fraction of quantitative variation are hypothesized to be the consequence of an altered dosage-sensitive regulatory system.
Effective Tumor Vaccine Generated by Fusion of Hepatoma Cells with Activated B Cells
Authors: Guo Yajun , Wu Mengchao , Chen Hen , Wang Xiaoning , Liu Guangluo , Li Guanglo , Ma Jing , Sy Man-Sun
Published: October 2006

Fusion of BERH-2 rat hepatocellular carcinoma cells with activated B cells produced hybrid cells that lost their tumorigenicity and became immunogenic. Syngeneic rats injected with BERH-2-B hybrid cells became resistant to challenge with parental BERH-2 cells, and rats with established BERH-2 hepatomas were cured by subsequent injection of BERH-2-B cells. Both CD4
+
and CD8
+
cells were essential for the induction of protective immunity; however, only CD8
+
cells were required for the eradication of BERH-2 tumors. The generation of hybrid tumor cells that elicit antitumor immune responses may be a useful strategy for cancer immunotherapy.
Requirement of Vascular Integrin α
v
β
3
for Angiogenesis
Authors: Brooks Peter C. , Clark Richard A. F. , Cheresh David A.
Published: October 2006

Angiogenesis depends on the adhesive interactions of vascular cells. The adhesion receptor integrin α
v
β
3
was identified as a marker of angiogenic vascular tissue. Integrin α
v
β
3
was expressed on blood vessels in human wound granulation tissue but not in normal skin, and it showed a fourfold increase in expression during angiogenesis on the chick chorioallantoic membrane. In the latter assay, a monoclonal antibody to α
v
β
3
blocked angiogenesis induced by basic fibroblast growth factor, tumor necrosis factor-α, and human melanoma fragments but had no effect on preexisting vessels. These findings suggest that α
v
β
3
may be a useful therapeutic target for diseases characterized by neovascularization.
Control of Cell Behavior During Vertebrate Development by
Slug
, a Zinc Finger Gene
Authors: Nieto M. Angela , Sargent Michael G. , Wilkinson David G. , Cooke Jonathan
Published: October 2006

Slug
, a vertebrate gene encoding a zinc finger protein of the Snail family, is expressed in the neural crest and in mesodermal cells emigrating from the primitive streak. Early chick embryos were incubated with antisense oligonucleotides to chick
Slug
. These oligonucleotides specifically inhibit the normal change in cell behavior that occurs at the two sites in the emerging body plan in which the gene is expressed. This change, which is the transition from epithelial to mesenchymal character, occurs at the formation of mesoderm during gastrulation and on emigration of the neural crest from the neural tube.
Crystal Structure of Rat DNA Polymerase β: Evidence for a Common Polymerase Mechanism
Authors: Sawaya Michael R. , Pelletier Huguette , Kumar Amalendra , Wilson Samuel H. , Kraut Joseph
Published: October 2006

Structures of the 31-kilodalton catalytic domain of rat DNA polymerase β (pol β) and the whole 39-kilodalton enzyme were determined at 2.3 and 3.6 angstrom resolution, respectively. The 31-kilodalton domain is composed of fingers, palm, and thumb subdomains arranged to form a DNA binding channel reminiscent of the polymerase domains of the Klenow fragment of
Escherichia coli
DNA polymerase I, HIV-1 reverse transcriptase, and bacteriophage T7 RNA polymerase. The amino-terminal 8-kilodalton domain is attached to the fingers subdomain by a flexible hinge. The two invariant aspartates found in all polymerase sequences and implicated in catalytic activity have the same geometric arrangement within structurally similar but topologically distinct palms, indicating that the polymerases have maintained, or possibly re-evolved, a common nucleotidyl transfer mechanism. The location of Mn
2+
and deoxyadenosine triphosphate in pol β confirms the role of the invariant aspartates in metal ion and deoxynucleoside triphosphate binding.
β
2
-Microglobulin-Independent MHC Class Ib Molecule Expressed by Human Intestinal Epithelium
Authors: Balk Steven P. , Burke Steven , Polischuk John E. , Frantz Martha E. , Yang Lin , Porcelli Steven , Colgan Sean P. , Blumberg Richard S.
Published: October 2006

A major histocompatibility complex class Ib protein, CD1d, is expressed by human intestinal epithelial cells (IECs) and is a ligand for CD8
+
T cells. CD1d was found to be expressed on the surface of human IECs as a 37-kilodalton protein that was β
2
-microglobulin (β
2
M) independent with no N-linked carbohydrate. Transfection into a β
2
M- cell line confirmed that CD1d could be expressed at the cell surface in the absence of β
2
M. These data indicate that IECs use a specialized pathway for CD1d synthesis and that a β
2
M-independent class Ib protein may be the normal ligand for some intestinal T cells.
Endothelial NOS and the Blockade of LTP by NOS Inhibitors in Mice Lacking Neuronal NOS
Authors: O'Dell Thomas J. , Huang Paul L. , Dawson Ted M. , Dinerman Jay L. , Snyder Solomon H. , Kandel Eric R. , Fishman Mark C.
Published: October 2006

Long-term potentiation (LTP) is a persistent increase in synaptic strength implicated in certain forms of learning and memory. In the CA1 region of the hippocampus, LTP is thought to involve the release of one or more retrograde messengers from the postsynaptic cell that act on the presynaptic terminal to enhance transmitter release. One candidate retrograde messenger is the membrane-permeant gas nitric oxide (NO), which in the brain is released after activation of the neuronal-specific NO synthase isoform (nNOS). To assess the importance of NO in hippocampal synaptic plasticity, LTP was examined in mice where the gene encoding nNOS was disrupted by gene targeting. In nNOS
-
mice, LTP induced by weak intensity tetanic stimulation was normal except for a slight reduction in comparison to that in wild-type mice and was blocked by NOS inhibitors, just as it was in wild-type mice. Immunocytochemical studies indicate that in the nNOS
-
mice as in wild-type mice, the endothelial form of NOS (eNOS) is expressed in CA1 neurons. These findings suggest that eNOS, rather than nNOS, generates NO within the postsynaptic cell during LTP.
Specific Interaction of Type I Receptors of the TGF-β Family with the Immunophilin FKBP-12
Authors: Wang Tongwen , Donahoe Patricia K. , Zervos Antonis S.
Published: October 2006

Transforming growth factor-β (TGF-β) family members bind to receptors that consist of heteromeric serine-threonine kinase subunits (type I and type II). In a yeast genetic screen, the immunophilin FKBP-12, a target of the macrolides FK506 and rapamycin, interacted with the type I receptor for TGF-β and with other type I receptors. Deletion, point mutation, and co-immunoprecipitation studies further demonstrated the specificity of the interaction. Excess FK506 competed with type I receptors for binding to FKBP-12, which suggests that these receptors share or overlap the macrolide binding site on FKBP-12, and therefore they may represent its natural ligand. The specific interaction between the type I receptors and FKBP-12 suggests that FKBP-12 may play a role in type I receptor-mediated signaling.
Mutations in
aquaporin-1
in Phenotypically Normal Humans Without Functional CHIP Water Channels
Authors: Preston Gregory M. , Smith Barbara L. , Zeidel Mark L. , Moulds John J. , Agre Peter
Published: October 2006

The gene
aquaporin-1
encodes channel-forming integral protein (CHIP), a member of a large family of water transporters found throughout nature. Three rare individuals were identified who do not express CHIP-associated Colton blood group antigens and whose red cells exhibit low osmotic water permeabilities. Genomic DNA analyses demonstrated that two individuals were homozygous for different nonsense mutations (exon deletion or frameshift), and the third had a missense mutation encoding a nonfunctioning CHIP molecule. Surprisingly, none of the three suffers any apparent clinical consequence, which raises questions about the physiological importance of CHIP and implies that other mechanisms may compensate for its absence.
RNA Editing: Transfer of Genetic Information from gRNA to Precursor mRNA in Vitro
Authors: Seiwert Scott D. , Stuart Kenneth
Published: October 2006

RNA editing in the mitochondrion of
Trypanosoma brucei
extensively alters the adenosine triphosphate synthase (ATPase) subunit 6 precursor messenger RNA (pre-mRNA) by addition of 447 uridines and removal of 28 uridines. In vivo, the guide RNA gA6[14] is thought to specify the deletion of two uridines from the editing site closest to the 3′ end. In this study, an in vitro system was developed that accurately removed uridines from this editing site in synthetic ATPase 6 pre-mRNA when gA6[14] and ATP were added. Mutations in both the guide RNA and the pre-mRNA editing site suggest that base-pairing interactions control the number of uridines deleted in vitro. Thus, guide RNAs are required for RNA editing and for the transfer of genetic information to pre-mRNAs.
Determination of Intrinsic Transcription Termination Efficiency by RNA Polymerase Elongation Rate
Authors: McDowell Jennifer C. , Roberts Jeffrey W. , Jin Ding Jun , Gross Carol
Published: October 2006

Transcription terminators recognized by several RNA polymerases include a DNA segment encoding uridine-rich RNA and, for bacterial RNA polymerase, a hairpin loop located immediately upstream. Here, mutationally altered
Escherichia coli
RNA polymerase enzymes that have different termination efficiencies were used to show that the extent of transcription through the uridine-rich encoding segment is controlled by the substrate concentration of nucleoside triphosphate. This result implies that the rate of elongation determines the probability of transcript release. Moreover, the position of release sites suggests an important spatial relation between the RNA hairpin and the boundary of the terminator.
Role of TCR ζ Chain in T Cell Development and Selection
Authors: Shores Elizabeth W. , Huang Kun , Tran Tom , Lee Eric , Grinberg Alexander , Love Paul E.
Published: October 2006

Signals mediated by the T cell receptor (TCR) are required for thymocyte maturation and selection. To examine the role of TCR ζ chain signals in development, TCR expression was restored in ζ-deficient mice with transgenic ζ chains that partially or completely lacked sequences required for signal transduction. The ζ chain played a role in thymic development by promoting TCR surface expression, but ζ-mediated signals were not essential because TCRs that contained signaling-deficient ζ chains promoted T cell maturation and transduced signals associated with thymic selection.
Resetting the Biological Clock: Mediation of Nocturnal Circadian Shifts by Glutamate and NO
Authors: Ding Jian M. , Chen Dong , Weber E. Todd , Faiman Lia E. , Rea Michael A. , Gillette Martha U.
Published: October 2006

Circadian rhythms of mammals are timed by an endogenous clock with a period of about 24 hours located in the suprachiasmatic nucleus (SCN) of the hypothalamus. Light synchronizes this clock to the external environment by daily adjustments in the phase of the circadian oscillation. The mechanism has been thought to involve the release of excitatory amino acids from retinal afferents to the SCN. Brief treatment of rat SCN in vitro with glutamate (Glu),
N
-methyl-D-aspartate (NMDA), or nitric oxide (NO) generators produced lightlike phase shifts of circadian rhythms. The SCN exhibited calcium-dependent nitric oxide synthase (NOS) activity. Antagonists of NMDA or NOS pathways blocked Glu effects in vitro, and intracerebroventricular injection of a NOS inhibitor in vivo blocked the light-induced resetting of behavioral rhythms. Together, these data indicate that Glu release, NMDA receptor activation, NOS stimulation, and NO production link light activation of the retina to cellular changes within the SCN mediating the phase resetting of the biological clock.
TLC1
: Template RNA Component of
Saccharomyces cerevisiae
Telomerase
Authors: Singer Miriam S. , Gottschling Daniel E.
Published: October 2006

Telomeres, the natural ends of linear eukaryotic chromosomes, are essential for chromosome stability. Because of the nature of DNA replication, telomeres require a specialized mechanism to ensure their complete duplication. Telomeres are also capable of silencing the transcription of genes that are located near them. In order to identify genes in the budding yeast
Saccharomyces cerevisiae
that are important for telomere function, a screen was conducted for genes that, when expressed in high amounts, would suppress telomeric silencing. This screen lead to the identification of the gene
TLC1
(
telomerase component 1
).
TLC1
encodes the template RNA of telomerase, a ribonucleoprotein required for telomere replication in a variety of organisms. The discovery of
TLC1
confirms the existence of telomerase in
S. cerevisiae
and may facilitate both the analysis of this enzyme and an understanding of telomere structure and function.
Reconstitution of Transcription Factor SL1: Exclusive Binding of TBP by SL1 or TFIID Subunits
Authors: Comai Lucio , Zomerdijk Joost C. B. M. , Beckmann Holger , Zhou Sharleen , Admon Arie , Tjian Robert
Published: October 2006

RNA polymerase I and II transcription factors SL1 and TFIID, respectively, are composed of the TATA-binding protein (TBP) and a set of TBP-associated factors (TAFs) responsible for promoter recognition. How the universal transcription factor TBP becomes committed to a TFIID or SL1 complex has not been known. Complementary DNAs encoding each of the three TAF
I
s that are integral components of SL1 have now been isolated. Analysis of subunit interactions indicated that the three TAF
I
s can bind individually and specifically to TBP. In addition, these TAF
I
s interact with each other to form a stable TBP-TAF complex. When TBP was bound first by either TAF
I
110, 63, or 48, subunits of TFIID such as TAF
II
250 and 150 did not bind TBP. Conversely, if TBP first formed a complex with TAF
II
250 or 150, the subunits of SL1 did not bind TBP. These results suggest that a mutually exclusive binding specificity for TBP intrinsic to SL1 and TFIID subunits directs the formation of promoter- and RNA polymerase-selective TBP-TAF complexes.
Binding and Stimulation of HIV-1 Integrase by a Human Homolog of Yeast Transcription Factor SNF5
Authors: Kalpana Ganjam V. , Marmon Shana , Wang Weidong , Crabtree Gerald R. , Goff Stephen P.
Published: October 2006

Upon entry into a host cell, retroviruses direct the reverse transcription of the viral RNA genome and the establishment of an integrated proviral DNA. The retroviral integrase protein (IN) is responsible for the insertion of the viral DNA into host chromosomal targets. The two-hybrid system was used to identify a human gene product that binds tightly to the human immunodeficiency virus-type 1 (HIV-1) integrase in vitro and stimulates its DNA-joining activity. The sequence of the gene suggests that the protein is a human homolog of yeast SNF5, a transcriptional activator required for high-level expression of many genes. The gene, termed
INI1
(for integrase interactor 1), may encode a nuclear factor that promotes integration and targets incoming viral DNA to active genes.
ATP-Dependent Nucleosome Reconfiguration and Transcriptional Activation from Preassembled Chromatin Templates
Authors: Pazin Michael J. , Kamakaka Rohinton T. , Kadonaga James T.
Published: October 2006

GAL4-VP16-mediated nucleosome reconfiguration and transcriptional activation were observed with preassembled chromatin templates that contained regular and physiological nucleosome spacing. Both processes were dependent on adenosine triphosphate (ATP), although binding of GAL4-VP16 to the chromatin was ATP-independent. Factor-mediated nucleosome reconfiguration was not, however, sufficient for transcriptional activation. These experiments recreate in vitro the active participation of nucleosomal cores in the regulation of transcription that occurs in vivo, and they suggest a multistep pathway for transcriptional activation in which factor- and ATP-dependent nucleosome reconfiguration is followed by facilitation by the DNA-bound activator of transcription from the repressed chromatin template.
Assembly of Transcriptionally Active RNA Polymerase I Initiation Factor SL1 from Recombinant Subunits
Authors: Zomerdijk Joost C. B. M. , Beckmann Holger , Comai Lucio , Tjian Robert
Published: October 2006

Initiation of ribosomal RNA synthesis by RNA polymerase I requires the promoter selectivity factor SL1, which consists of the TATA-binding protein, TBP, and three associated factors, TAF
I
s 110, 63, and 48. Here the in vivo and in vitro assembly of functional SL1 complexes from recombinant TAF
I
s and TBP are reported. Complexes containing TBP and all three TAF
I
s were as active in supporting transcription from the human ribosomal RNA gene promoter as endogenous SL1, whereas partial complexes without TBP did not efficiently direct transcription in vitro. These results suggest that TAF
I
s 110, 63, and 48, together with TBP, are necessary and sufficient to reconstitute a transcriptionally active SL1 complex.
Activation of Raf as a Result of Recruitment to the Plasma Membrane
Authors: Stokoe David , Macdonald Susan G. , Cadwallader Karen , Symons Marc , Hancock John F.
Published: October 2006

The small guanine nucleotide binding protein Ras participates in a growth promoting signal transduction pathway. The mechanism by which interaction of Ras with the protein kinase Raf leads to activation of Raf was studied. Raf was targeted to the plasma membrane by addition of the COOH-terminal localization signals of K-ras. This modified form of Raf (RafCAAX) was activated to the same extent as Raf coexpressed with oncogenic mutant Ras. Plasma membrane localization rather than farnesylation or the presence of the additional COOH-terminal sequence accounted for the activation of RafCAAX. The activation of RafCAAX was completely independent of Ras; it was neither potentiated by oncogenic mutant Ras nor abrogated by dominant negative Ras. Raf, once recruited to the plasma membrane, was not anchored there by Ras; most activated Raf in cells was associated with plasma membrane cytoskeletal elements, not the lipid bilayer. Thus, Ras functions in the activation of Raf by recruiting Raf to the plasma membrane where a separate, Ras-independent, activation of Raf occurs.
Cell Membrane Resealing by a Vesicular Mechanism Similar to Neurotransmitter Release
Authors: Steinhardt Richard A. , Bi Guoqiang , Alderton Janet M.
Published: October 2006

After injury to the cell membrane, rapid resealing of the membrane occurs with little loss of intracellular contents. This process has been studied by measurement of the rate of dye loss after membrane puncture in both the sea urchin embryo and 3T3 fibroblasts. Resealing of disrupted cell membranes requires external calcium that can be antagonized by magnesium. Block of multifunctional calcium/calmodulin kinase, which regulates exocytotic vesicle availability at synapses, and of kinesin, which is required for outward-directed transport of vesicles, inhibited membrane resealing. Resealing was also inhibited by botulinum neurotoxins B and A, suggesting that the two synaptosomal-associated proteins synaptobrevin and SNAP-25 also participate in resealing. This pattern of inhibition indicates that the calcium-dependent mechanisms for cell membrane resealing may involve vesicle delivery, docking, and fusion, similar to the exocytosis of neurotransmitters.
The Adjuvant Effect of Interleukin-12 in a Vaccine Against
Leishmania major
Authors: Afonso Luis C. C. , Scharton Tanya M. , Vieira Leda Q. , Wysocka Maria , Trinchieri Giorgio , Scott Phillip
Published: October 2006

Protection induced by vaccination depends on the capacity of the vaccine to elicit an appropriate immune response. In leishmaniasis, protection requires leishmanial-specific CD4
+
T helper (T
H
) cells. Vaccination of BALB/c mice with leishmanial antigens and interleukin-12 (IL-12) promoted the development of leishmanial-specific CD4
+
T
H
1 cells. These mice were resistant to subsequent infection with
Leishmania major
. Thus, IL-12 is an effective adjuvant for the initiation of protective cell-mediated immunity against leishmaniasis and may be an important component in other vaccines that need to induce cell-mediated immunity.
Visualization of Quantal Synaptic Transmission by Dendritic Calcium Imaging
Authors: Murphy Timothy H. , Baraban Jay M. , Wier W. Gil , Blatter Lothar A.
Published: October 2006

As changes in synaptic strength are thought to be critical for learning and memory, it would be useful to monitor the activity of individual identified synapses on mammalian central neurons. Calcium imaging of cortical neurons grown in primary culture was used to visualize the activation of individual postsynaptic elements by miniature excitatory synaptic currents elicited by spontaneous quantal release. This approach revealed that the probability of spontaneous activity differed among synapses on the same dendrite. Furthermore, synapses that undergo changes in activity induced by glutamate or phorbol ester treatment were identified.
Mesodermal Patterning by a Gradient of the Vertebrate Homeobox Gene
goosecoid
Authors: Niehrs Christof , Steinbeisser Herbert , De Robertis Eddy M.
Published: October 2006

Amphibian mesoderm arises from the marginal zone of the early gastrula and generates various tissues such as notochord, muscle, kidney, and blood. Small changes (twofold) in the amount of microinjected messenger RNA encoding the
goosecoid
(
gsc
) homeodomain protein resulted in marked changes in the differentiation of mesoderm in
Xenopus laevis
. At least three thresholds were observed, which were sufficient to specify four mesodermal cell states. Endogenous
gsc
messenger RNA was expressed in the marginal zone in a graded fashion that is congruent with a role for this gene in dorso-ventral patterning of mesoderm at the early gastrula stage.
Requirement for BDNF in Activity-Dependent Survival of Cortical Neurons
Authors: Ghosh Anirvan , Carnahan Josette , Greenberg Michael E.
Published: October 2006

Cultured embryonic cortical neurons from rats were used to explore mechanisms of activity-dependent neuronal survival. Cell survival was increased by the activation of voltage-sensitive calcium channels (VSCCs) but not by activation of
N
-methyl-D-aspartate receptors. These effects correlated with the expression of brain-derived neurotrophic factor (BDNF) induced by these two classes of calcium channels. Antibodies to BDNF (which block intracellular signaling by BDNF, but not by nerve growth factor, NT3, or NT4/5) reduced the survival of cortical neurons and reversed the VSCC-mediated increase in survival. Thus, endogenous BDNF is a trophic factor for cortical neurons whose expression is VSCC-regulated and that functions in the VSCC-dependent survival of these neurons.
[URE3] as an Altered
URE2
Protein: Evidence for a Prion Analog in
Saccharomyces cerevisiae
Authors: Wickner Reed B.
Published: October 2006

A cytoplasmically inherited element, [URE3], allows yeast to use ureidosuccinate in the presence of ammonium ion. Chromosomal mutations in the
URE2
gene produce the same phenotype. [URE3] depends for its propagation on the
URE2
product (Ure2p), a negative regulator of enzymes of nitrogen metabolism.
Saccharomyces cerevisiae
strains cured of [URE3] with guanidium chloride were shown to return to the [URE3]-carrying state without its introduction from other cells. Overproduction of Ure2p increased the frequency with which a strain became [URE3] by 100-fold. In analogy to mammalian prions, [URE3] may be an altered form of Ure2p that is inactive for its normal function but can convert normal Ure2p to the altered form. The genetic evidence presented here suggests that protein-based inheritance, involving a protein unrelated to the mammalian prion protein, can occur in a microorganism.
Arabidopsis
ABA Response Gene
ABI1
: Features of a Calcium-Modulated Protein Phosphatase
Authors: Leung Jeffrey , Bouvier-Durand Michelle , Morris Peter-Christian , Guerrier Danièle , Chefdor Françoise , Giraudat Jérôme
Published: October 2006

The
Arabidopsis
ABI1
locus is essential for a wide spectrum of abscisic acid (ABA) responses throughout plant development. Here,
ABI1
was shown to regulate stomatal aperture in leaves and mitotic activity in root meristems. The
ABI1
gene was cloned and predicted to encode a signaling protein. Although its carboxyl-terminal domain is related to serine-threonine phosphatase 2C, the ABI1 protein has a unique amino-terminal extension containing an EF hand calcium-binding site. These results suggest that the ABI1 protein is a Ca
2+
-modulated phosphatase and functions to integrate ABA and Ca
2+
signals with phosphorylation-dependent response pathways.
Pattern Formation and Eyespot Determination in Butterfly Wings
Authors: Carroll Sean B. , Gates Julie , Keys David N. , Paddock Stephen W. , Panganiban Grace E. F. , Selegue Jane E. , Williams Jim A.
Published: October 2006

Butterfly wings display pattern elements of many types and colors. To identify the molecular processes underlying the generation of these patterns, several butterfly cognates of
Drosophila
appendage patterning genes have been cloned and their expression patterns have been analyzed. Butterfly wing patterns are organized by two spatial coordinate systems. One system specifies positional information with respect to the entire wing field and is conserved between fruit flies and butterflies. A second system, superimposed on the general system and involving several of the same genes, operates within each wing subdivision to elaborate discrete pattern elements. Eyespots, which form from discrete developmental organizers, are marked by
Distal-less
gene expression. These circular pattern elements appear to be generated by a process similar to, and perhaps evolved from, proximodistal pattern formation in insect appendages.
Symmetric Complexes of GroE Chaperonins as Part of the Functional Cycle
Authors: Schmidt Marion , Rutkat Kerstin , Rachel Reinhard , Pfeifer Günter , Jaenicke Rainer , Viitanen Paul , Lorimer George , Buchner Johannes
Published: October 2006

The particular structural arrangement of chaperonins probably contributes to their ability to assist in the folding of proteins. The interaction of the oligomeric bacterial chaperonin GroEL and its cochaperonin, GroES, in the presence of adenosine diphosphate (ADP) forms an asymmetric complex. However, in the presence of adenosine triphosphate (ATP) or its nonhydrolyzable analogs, symmetric complexes were found by electron microscopy and image analysis. The existence of symmetric chaperonin complexes is not predicted by current models of the functional cycle for GroE-mediated protein folding. Because complete folding of a nonnative substrate protein in the presence of GroEL and GroES only occurs in the presence of ATP, but not with ADP, the symmetric chaperonin complexes formed during the GroE cycle are proposed to be functionally significant.
Homology of the
eyeless
Gene of
Drosophila
to the
Small eye
Gene in Mice and
Aniridia
in Humans
Authors: Quiring Rebecca , Walldorf Uwe , Kloter Urs , Gehring Walter J.
Published: October 2006

A
Drosophila
gene that contains both a paired box and a homeobox and has extensive sequence homology to the mouse
Pax-6
(
Small eye
) gene was isolated and mapped to chromosome IV in a region close to the
eyeless
locus. Two spontaneous mutations,
ey
2
and
ey
R
, contain transposable element insertions into the cloned gene and affect gene expression, particularly in the eye primordia. This indicates that the cloned gene encodes
ey
. The finding that
ey
of
Drosophila
,
Small eye
of the mouse, and human
Aniridia
are encoded by homologous genes suggests that eye morphogenesis is under similar genetic control in both vertebrates and insects, in spite of the large differences in eye morphology and mode of development.
Blockage of NF-κB Signaling by Selective Ablation of an mRNA target by 2-5A Antisense Chimeras
Authors: Maran Avudaiappan , Maitra Ratan K. , Kumar Aseem , Dong Beihua , Xiao Wei , Li Guiying , Williams Bryan R. G. , Torrence Paul F. , Silverman Robert H.
Published: October 2006

Activation of 2-5A-dependent ribonuclease by 5′-phosphorylated, 2′,5′-linked oligoadenylates, known as 2-5A, is one pathway of interferon action. Unaided uptake into HeLa cells of 2-5A linked to an antisense oligonucleotide resulted in the selective ablation of messenger RNA for the double-stranded RNA (dsRNA)-dependent protein kinase PKR. Similarly, purified, recombinant human 2-5A-dependent ribonuclease was induced to selectively cleave PKR messenger RNA. Cells depleted of PKR activity were unresponsive to activation of nuclear factor-κB (NF-κB) by the dsRNA poly(I):poly(C), which provides direct evidence that PKR is a transducer for the dsRNA signaling of NF-κB.
The Mobile Flavin of 4-OH Benzoate Hydroxylase
Authors: Gatti Domenico L. , Palfey Bruce A. , Lah Myoung Soo , Entsch Barrie , Massey Vincent , Ballou David P. , Ludwig Martha L.
Published: October 2006

Para
-hydroxybenzoate hydroxylase inserts oxygen into substrates by means of the labile intermediate, flavin C(4a)-hydroperoxide. This reaction requires transient isolation of the flavin and substrate from the bulk solvent. Previous crystal structures have revealed the position of the substrate
para
-hydroxybenzoate during oxygenation but not how it enters the active site. In this study, enzyme structures with the flavin ring displaced relative to the protein were determined, and it was established that these or similar flavin conformations also occur in solution. Movement of the flavin appears to be essential for the translocation of substrates and products into the solvent-shielded active site during catalysis.
Phosphate-Regulated Inactivation of the Kinase PHO80-PHO85 by the CDK Inhibitor PHO81
Authors: Schneider Ken R. , Smith Rebecca L. , O'Shea Erin K.
Published: October 2006

A complex consisting of the cyclin-dependent kinase (CDK) PHO85 and the cyclin PHO80 phosphorylates and is thought to inactivate the transcription factor PHO4 when yeast cells are grown in medium containing high concentrations of phosphate. The CDK inhibitor PHO81 inhibits the kinase activity of the PHO80-PHO85 complex when
Saccharomyces cerevisiae
cells are grown in medium depleted of phosphate. A region of PHO81 with similarity to the mammalian CDK inhibitor p16
INK4
is sufficient for inhibition in vitro. These studies demonstrate that CDK inhibitors are used to regulate kinases involved in processes other than cell cycle control and suggest that the ankyrin repeat motif may be commonly used for interaction with cyclin-CDK complexes.
Interaction of the Protein Kinase Raf-1 with 14-3-3 Proteins
Authors: Fu Haian , Xia Kai , Pallas David C. , Cui Can , Conroy Karen , Narsimhan Radha P. , Mamon Harvey , Collier R. John , Roberts Thomas M.
Published: October 2006

Members of a family of highly conserved proteins, termed 14-3-3 proteins, were found by several experimental approaches to associate with Raf-1, a central component of a key signal transduction pathway. Optimal complex formation required the amino-terminal regulatory domain of Raf-1. The association of 14-3-3 proteins and Raf-1 was not substantially affected by the activation state of Raf.
Association of the Protein Kinases c-Bcr and Bcr-Abl with Proteins of the 14-3-3 Family
Authors: Reuther Gary W. , Fu Haian , Cripe Larry D. , Collier R. John , Pendergast Ann Marie
Published: October 2006

In this study, a protein that interacts with sequences encoded by the first exon of the protein kinase Bcr was cloned. The Bcr-associated protein 1 (Bap-1) is a member of the 14-3-3 family of proteins. Bap-1 interacts with full-length c-Bcr and with the chimeric Bcr-Abl tyrosine kinase of Philadelphia chromosome (Ph
1
)-positive human leukemias. Bap-1 is a substrate for the Bcr serine-threonine kinase and is also phosphorylated on tyrosine by Bcr-Abl but not by c-Abl. Bap-1 may function in the regulation of c-Bcr and may contribute to the transforming activity of Bcr-Abl in vivo. 14-3-3 proteins are essential for cell proliferation and have a role in determining the timing of mitosis in yeast. Through direct binding to sequences present in Bcr and in other proteins implicated in signaling, the mammalian 14-3-3 proteins may link specific signaling protein components to mitogenic and cell-cycle control pathways.
Intermolecular Forces and Energies Between Ligands and Receptors
Authors: Moy Vincent T. , Florin Ernst-Ludwig , Gaub Hermann E.
Published: October 2006

The recognition mechanisms and dissociation pathways of the avidin-biotin complex and of actin monomers in actin filaments were investigated. The unbinding forces of discrete complexes of avidin or streptavidin with biotin analogs are proportional to the enthalpy change of the complex formation but independent of changes in the free energy. This result indicates that the unbinding process is adiabatic and that entropic changes occur after unbinding. On the basis of the measured forces and binding energies, an effective rupture length of 9.5 ± 1 angstroms was calculated for all biotin-avidin pairs and approximately 1 to 3 angstroms for the actin monomer-monomer interaction. A model for the correlation among binding forces, intermolecular potential, and molecular function is proposed.
Insertion of a Coiled-Coil Peptide from Influenza Virus Hemagglutinin into Membranes
Authors: Yu Yeon Gyu , King David S. , Shin Yeon-Kyun
Published: October 2006

The trimeric protein hemagglutinin (HA) of the influenza viral envelope is essential for cell entry. To investigate the interaction of HA with membranes, two 40-residue, cysteine-substituted peptides comprising the loop region and the first part of the coiled-coil stem were synthesized and modified with a nitroxide spin label. Electron paramagnetic resonance analysis revealed that the peptide inserts reversibly into phospholipid vesicles under endosomal pH conditions. This result suggests that some or all of the long coiled-coil trimer of HA may insert into membranes, which could bring the viral and cell membranes closer together and facilitate fusion.
Abnormal Fear Response and Aggressive Behavior in Mutant Mice Deficient for α-Calcium-Calmodulin Kinase II
Authors: Chen Chong , Rainnie Donald G. , Greene Robert W. , Tonegawa Susumu
Published: October 2006

Mice deficient for the gene encoding α-calcium-calmodulin-dependent kinase II (α-CaMKII knockout mice) provide a promising tool to link behavioral and cellular abnormalities with a specific molecular lesion. The heterozygous mouse exhibited a well-circumscribed syndrome of behavioral abnormalities, consisting primarily of a decreased fear response and an increase in defensive aggression, in the absence of any measured cognitive deficits. Unlike the heterozygote, the homozygote displayed abnormal behavior in all paradigms tested. At the cellular level, both extracellular and whole-cell patch clamp recordings indicated that serotonin release in putative serotonergic neurons of the dorsal raphe was reduced. Thus, α-CaMKII knockout mice, in particular the heterozygote, may provide a model for studying the molecular and cellular basis underlying emotional disorders involving fear and aggression.
Internal Lysine Palmitoylation in Adenylate Cyclase Toxin from
Bordetella pertussis
Authors: Hackett Murray , Guo Lin , Shabanowitz Jeffrey , Hunt Donald F. , Hewlett Erik L.
Published: October 2006

A number of bacterial protein toxins, including adenylate cyclase (AC) toxin from
Bordetella pertussis
, require the product of an accessory gene in order to express their biological activities. In this study, mass spectrometry was used to demonstrate that activated, wild-type AC toxin was modified by amide-linked palmitoylation on the ε-amino group of lysine 983. This modification was absent from a mutant in which the accessory gene had been disrupted. A synthetic palmitoylated peptide corresponding to the tryptic fragment (glutamine 972 to arginine 984) that contained the acylation blocked AC toxin-induced accumulation of adenosine 3′,5′-monophosphate, whereas the non-acylated peptide had no effect.
Vertebrate Embryonic Induction: Mesodermal and Neural Patterning
Authors: Kessler Daniel S. , Melton Douglas A.
Published: October 2006

Within the fertilized egg lies the information necessary to generate a diversity of cell types in the precise pattern of tissues and organs that comprises the vertebrate body. Seminal embryological experiments established the importance of induction, or cell interactions, in the formation of embryonic tissues and provided a foundation for molecular studies. In recent years, secreted gene products capable of inducing or patterning embryonic tissues have been identified. Despite these advances, embryologists remain challenged by fundamental questions: What are the endogenous inducing molecules? How is the action of an inducer spatially and temporally restricted? How does a limited group of inducers give rise to a diversity of tissues? In this review, the focus is on the induction and patterning of mesodermal and neural tissues in the frog
Xenopus laevis
, with an emphasis on families of secreted molecules that appear to underlie inductive events throughout vertebrate embryogenesis.
Design of a G⋅C-Specific DNA Minor Groove-Binding Peptide
Authors: Geierstanger Bernhard H. , Mrksich Milan , Dervan Peter B. , Wemmer David E.
Published: October 2006

A four-ring tripeptide containing alternating imidazole and pyrrole carboxamides specifically binds six-base pair 5′-(A,T)GCGC(A,T)-3′ sites in the minor groove of DNA. The designed peptide has a specificity completely reversed from that of the tripyrrole distamycin, which binds A,T sequences. Structural studies with nuclear magnetic resonance revealed that two peptides bound side-by-side and in an antiparallel orientation in the minor groove. Each of the four imidazoles in the 2:1 ligand-DNA complex recognized a specific guanine amino group in the GCGC core through a hydrogen bond. Targeting a designated four-base pair G⋅C tract by this synthetic ligand supports the generality of the 2:1 peptide-DNA motif for sequence-specific minor groove recognition of DNA.
Interaction of a Protein Phosphatase with an
Arabidopsis
Serine-Threonine Receptor Kinase
Authors: Stone Julie M. , Collinge Margaret A. , Smith Robert D. , Horn Mark A. , Walker John C.
Published: October 2006

A protein phosphatase was cloned that interacts with a serine-threonine receptor-like kinase, RLK5, from
Arabidopsis thaliana
. The phosphatase, designated KAPP (kinase-associated protein phosphatase), is composed of three domains: an amino-terminal signal anchor, a kinase interaction (KI) domain, and a type 2C protein phosphatase catalytic region. Association of RLK5 with the KI domain is dependent on phosphorylation of RLK5 and can be abolished by dephosphorylation. KAPP may function as a signaling component in a pathway involving RLK5.