bluuebunny/crossref_metadata_2025 huggingface dataset:
Arabidopsis
disrupted in
SQD2
encoding sulfolipid synthase is impaired in phosphate-limited growth
Authors: Yu Bin , Xu Changcheng , Benning Christoph
Published: July 2002

The sulfolipid sulfoquinovosyldiacylglycerol is one of the three nonphosphorous glycolipids that provide the bulk of the structural lipids in photosynthetic membranes of seed plants. Unlike the galactolipids, sulfolipid is anionic at physiological pH because of its 6-deoxy-6-sulfonate-glucose (sulfoquinovose) head group. The biosynthesis of this lipid proceeds in two steps: first, the assembly of UDP-sulfoquinovose from UDP-glucose and sulfite, and second, the transfer of the sulfoquinovose moiety from UDP-sulfoquinovose to diacylglycerol. The first reaction is catalyzed by the SQD1 protein in
Arabidopsis
. Here we describe the identification of the
SQD2
gene of
Arabidopsis
. We propose that this gene encodes the sulfoquinovosyltransferase catalyzing the second step of sulfolipid biosynthesis. Expression of
SQD1
and
SQD2
in
Escherichia coli
reconstituted plant sulfolipid biosynthesis in this bacterium. Insertion of a transfer DNA into this gene in
Arabidopsis
led to complete lack of sulfolipid in the respective
sqd2
mutant. This mutant showed reduced growth under phosphate-limited growth conditions. The results support the hypothesis that sulfolipid can function as a substitute of anionic phospholipids under phosphate-limited growth conditions. Along with phosphatidylglycerol, sulfolipid contributes to maintaining a negatively charged lipid–water interface, which presumably is required for proper function of photosynthetic membranes.
The intranuclear prolactin/cyclophilin B complex as a transcriptional inducer
Authors: Rycyzyn Michael A. , Clevenger Charles V.
Published: July 2002

The nuclear translocation of peptide hormones, such as the somatolactogenic hormone prolactin, after receptor internalization has been widely reported. Prolactin has been demonstrated to interact with cyclophilin B, a member of the immunophilin family of proteins. Cyclophilin B interaction with prolactin potentiated prolactin-induced proliferation, cell growth, and the nuclear retrotransport of prolactin. These effects could be abrogated by the removal of the peptidyl-prolyl isomerase activity of cyclophilin B. Our findings indicate that the intranuclear prolactin/cyclophilin B complex acts as a transcriptional inducer by interacting directly with Stat5, resulting in the removal of the Stat-repressor protein inhibitor of activated Stat 3 (PIAS3), thereby enhancing Stat5 DNA-binding activity and prolactin-induced, Stat5-mediated gene expression.
An efficient recombination system for chromosome engineering in
Escherichia coli
Authors: Yu Daiguan , Ellis Hilary M. , Lee E-Chiang , Jenkins Nancy A. , Copeland Neal G. , Court Donald L.
Published: July 2002

A recombination system has been developed for efficient chromosome
engineering in
Escherichia coli
by using electroporated
linear DNA. A defective λ prophage supplies functions that protect
and recombine an electroporated linear DNA substrate in the bacterial
cell. The use of recombination eliminates the requirement for standard
cloning as all novel joints are engineered by chemical synthesis
in vitro
and the linear DNA is efficiently recombined
into place
in vivo
. The technology and manipulations
required are simple and straightforward. A temperature-dependent
repressor tightly controls prophage expression, and, thus,
recombination functions can be transiently supplied by shifting
cultures to 42°C for 15 min. The efficient prophage recombination
system does not require host RecA function and depends primarily on
Exo, Beta, and Gam functions expressed from the defective λ prophage.
The defective prophage can be moved to other strains and can be easily
removed from any strain. Gene disruptions and modifications of both the
bacterial chromosome and bacterial plasmids are possible. This system
will be especially useful for the engineering of large bacterial
plasmids such as those from bacterial artificial chromosome libraries.
Dynamic actin filaments are required for stable long-term potentiation (LTP) in area CA1 of the hippocampus
Authors: Krucker Thomas , Siggins George R. , Halpain Shelley
Published: July 2002

The hypothesis that dynamic actin filaments participate in specific aspects of synaptic plasticity was investigated at the Schaffer-collateral-CA1 pyramidal cell synapse of mouse hippocampus. Low concentrations (0.01–1 μM) of compounds that inhibit actin filament assembly were bath applied to hippocampal slices during extracellular recording of field excitatory postsynaptic potentials. Cytochalasin D, cytochalasin B, and latrunculin A all impaired the maintenance of LTP induced by brief high-frequency stimulation. This effect on LTP maintenance was specific, because none of the compounds affected basal synaptic transmission, paired-pulse facilitation, LTP induction, or post-tetanic potentiation. The effect of cytochalasin B was reversible. The results are consistent with a model in which dynamic actin filaments play an essential role in the molecular mechanisms underlying the early maintenance phase of LTP, such as growth of new synaptic connections or conversion of silent synapses.
Do lampreys have lymphocytes? The Spi evidence
Authors: Shintani Seikou , Terzic Janos , Sato Akie , Saraga-Babic Mirna , O'hUigin Colm , Tichy Herbert , Klein Jan
Published: July 2002

It is generally accepted that living jawless vertebrates (lampreys and hagfishes) lack the capability of mounting an adaptive immune response. At the same time, however, there are reports describing histological evidence for the presence in agnathan tissues of lymphocytes, the key players in adaptive immunity. The question therefore arises whether the cells identified morphologically as lymphocytes are true lymphocytes in terms of their genetic developmental program. In this study, evidence is provided that the lampreys express a member of the purine box 1 (
PU
.1
)/spleen focus-forming virus integration B (
Spi-B
) gene family known to be critically and specifically involved in the differentiation of lymphocytes in jawed vertebrates. The lamprey gene is expressed in the lymphocyte-like cells of the digestive tract and inexplicably also in the ovary.
Effects of sampling standardization on estimates of Phanerozoic marine diversification
Authors: Alroy J. , Marshall C. R. , Bambach R. K. , Bezusko K. , Foote M. , Fürsich F. T. , Hansen T. A. , Holland S. M. , Ivany L. C. , Jablonski D. , Jacobs D. K. , Jones D. C. , Kosnik M. A. , Lidgard S. , Low S. , Miller A. I. , Novack-Gottshall P. M. , Olszewski T. D. , Patzkowsky M. E. , Raup D. M. , Roy K. , Sepkoski J. J. , Sommers M. G. , Wagner P. J. , Webber A.
Published: July 2002

Global diversity curves reflect more than just the number of taxa
that have existed through time: they also mirror variation in the
nature of the fossil record and the way the record is reported. These
sampling effects are best quantified by assembling and analyzing large
numbers of locality-specific biotic inventories. Here, we introduce a
new database of this kind for the Phanerozoic fossil record of marine
invertebrates. We apply four substantially distinct analytical methods
that estimate taxonomic diversity by quantifying and correcting for
variation through time in the number and nature of inventories.
Variation introduced by the use of two dramatically different counting
protocols also is explored. We present sampling-standardized diversity
estimates for two long intervals that sum to 300 Myr (Middle
Ordovician-Carboniferous; Late Jurassic-Paleogene). Our new curves
differ considerably from traditional, synoptic curves. For example,
some of them imply unexpectedly low late Cretaceous and early Tertiary
diversity levels. However, such factors as the current emphasis in the
database on North America and Europe still obscure our view of the
global history of marine biodiversity. These limitations will be
addressed as the database and methods are refined.
Negative frequency-dependent selection maintains a dramatic flower color polymorphism in the rewardless orchid
Dactylorhiza sambucina
(L.) Soò
Authors: Gigord Luc D. B. , Macnair Mark R. , Smithson Ann
Published: July 2002

The orchid
Dactylorhiza sambucina
shows a stable and
dramatic flower-color polymorphism, with both yellow- and
purple-flowered individuals present in natural populations throughout
the range of the species in Europe. The evolutionary significance of
flower-color polymorphisms found in many rewardless orchid species has
been discussed at length, but the mechanisms responsible for their
maintenance remain unclear. Laboratory experiments have suggested that
behavioral responses by pollinators to lack of reward availability
might result in a reproductive advantage for rare-color morphs.
Consequently, we performed an experiment varying the relative frequency
of the two color morphs of
D. sambucina
to test whether
rare morph advantage acted in the natural habitat of the species. We
show here clear evidence from this manipulative experiment that
rare-color morphs have reproductive advantage through male and
female components. This is the first demonstration, to our knowledge,
that negative frequency-dependent selection through pollinator
preference for rare morphs can cause the maintenance of a flower-color
polymorphism.
Dimerization and the effectiveness of ICAM-1 in mediating LFA-1-dependent adhesion
Authors: Jun Chang-Duk , Shimaoka Motomu , Carman Christopher V. , Takagi Junichi , Springer Timothy A.
Published: July 2002

Dimeric intercellular adhesion molecule-1 (ICAM-1) binds more efficiently to lymphocyte function-associated antigen-1 (LFA-1) than monomeric ICAM-1. However, it is unknown whether dimerization enhances binding simply by providing two ligand-binding sites and thereby increasing avidity, or whether it serves to generate a single “fully competent” LFA-1-binding surface. Domain 1 of ICAM-1 contains both the binding site for LFA-1, centered on residue E34, and a homodimerization interface. Whether the LFA-1-binding site extends across the homodimerization interface has not been tested. To address this question, we constructed four different heterodimeric soluble forms of ICAM-1 joined at the C terminus via an α-helical coiled coil (ACID-BASE). These heterodimeric ICAM-1 constructs include, (i) E34/E34 (two intact LFA-1-binding sites), (ii) E34/K34 (one disrupted LFA-1-binding site), (iii) E34/ΔD1–2 (one deleted LFA-1-binding site), and (iv) K34/K34 (two disrupted LFA-1-binding sites). Cells bearing activated LFA-1 bound similarly to surfaces coated with either E34/K34 or E34/ΔD1–2 and with an ≈2-fold reduction in efficiency compared with E34/E34, suggesting that D1 dimerization, which is precluded in E34/ΔD1-D2, is not necessary for optimal LFA-1 binding. Furthermore, BIAcore (BIAcore, Piscataway, NJ) affinity measurements revealed that soluble open LFA-1 I domain bound to immobilized soluble ICAM-1, E34/E34, E34/K34, and E34/ΔD1-D2 with nearly identical affinities. These studies demonstrate that a single ICAM-1 monomer, not dimeric ICAM-1, represents the complete, “fully competent” LFA-1-binding surface.
Wheat leaves emit nitrous oxide during nitrate assimilation
Authors: Smart David R. , Bloom Arnold J.
Published: July 2002

Nitrous oxide (N2O) is a key atmospheric greenhouse gas that contributes to global climatic change through radiative warming and depletion of stratospheric ozone. In this report, N2O flux was monitored simultaneously with photosynthetic CO2and O2exchanges from intact canopies of 12 wheat seedlings. The rates of N2O-N emitted ranged from <2 pmol⋅m−2⋅s−1when NH\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} \begin{equation*}{\mathrm{_{4}^{+}}}\end{equation*}\end{document}was the N source, to 25.6 ± 1.7 pmol⋅m−2⋅s−1(mean ± SE,n= 13) when the N source was shifted to NO\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} \begin{equation*}{\mathrm{_{3}^{-}}}\end{equation*}\end{document}. Such fluxes are among the smallest reported for any trace gas emitted by a higher plant. Leaf N2O emissions were correlated with leaf nitrate assimilation activity, as measured by using the assimilation quotient, the ratio of CO2assimilated to O2evolved.15N isotopic signatures on N2O emitted from leaves supported direct N2O production by plant NO\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} \begin{equation*}{\mathrm{_{3}^{-}}}\end{equation*}\end{document}assimilation and not N2O produced by microorganisms on root surfaces and emitted in the transpiration stream.In vitroproduction of N2O by both intact chloroplasts and nitrite reductase, but not by nitrate reductase, indicated that N2O produced by leaves occurred during photoassimilation of NO\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} \begin{equation*}{\mathrm{_{2}^{-}}}\end{equation*}\end{document}in the chloroplast. Given the large quantities of NO\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} \begin{equation*}{\mathrm{_{3}^{-}}}\end{equation*}\end{document}assimilated by plants in the terrestrial biosphere, these observations suggest that formation of N2O during NO\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} \begin{equation*}{\mathrm{_{2}^{-}}}\end{equation*}\end{document}photoassimilation could be an important global biogenic N2O source.
Subnuclear targeting of Runx/Cbfa/AML factors is essential for tissue-specific differentiation during embryonic development
Authors: Choi Je-Yong , Pratap Jitesh , Javed Amjad , Zaidi S. Kaleem , Xing Lianping , Balint Eva , Dalamangas Sara , Boyce Brendan , van Wijnen André J. , Lian Jane B. , Stein Janet L. , Jones Stephen N. , Stein Gary S.
Published: July 2002

Runx (Cbfa/AML) transcription factors are critical for tissue-specific gene expression. A unique targeting signal in the C terminus directs Runx factors to discrete foci within the nucleus. Using Runx2/CBFA1/AML3 and its essential role in osteogenesis as a model, we investigated the fundamental importance of fidelity of subnuclear localization for tissue differentiating activity by deleting the intranuclear targeting signal via homologous recombination. Mice homozygous for the deletion (Runx2ΔC) do not form bone due to maturational arrest of osteoblasts. Heterozygotes do not develop clavicles, but are otherwise normal. These phenotypes are indistinguishable from those of the homozygous and heterozygous null mutants, indicating that the intranuclear targeting signal is a critical determinant for function. The expressed truncated Runx2ΔC protein enters the nucleus and retains normal DNA binding activity, but shows complete loss of intranuclear targeting. These results demonstrate that the multifunctional N-terminal region of the Runx2 protein is not sufficient for biological activity. We conclude that subnuclear localization of Runx factors in specific foci together with associated regulatory functions is essential for control of Runx-dependent genes involved in tissue differentiation during embryonic development.
A46R and A52R from vaccinia virus are antagonists of host IL-1 and toll-like receptor signaling
Authors: Bowie Andrew , Kiss-Toth Endre , Symons Julian A. , Smith Geoffrey L. , Dower Steven K. , O'Neill Luke A. J.
Published: July 2002

Poxviruses employ many strategies to evade and neutralize the host immune response. In this study, we have identified two vaccinia virus ORFs, termed A46R and A52R, that share amino acid sequence similarity with the Toll/IL-1 receptor (TIR) domain, a motif that defines the IL-1/Toll-like receptor (TLR) superfamily of receptors, which have a key role in innate immunity and inflammation. When expressed in mammalian cells, the protein products of both ORFs were shown to interfere specifically with IL-1 signal transduction. A46R partially inhibited IL-1-mediated activation of the transcription factor NFκB, and A52R potently blocked both IL-1- and TLR4-mediated NFκB activation. MyD88 is a TIR domain-containing adapter molecule known to have a central role in both IL-1 and TLR4 signaling. A52R mimicked the dominant-negative effect of a truncated version of MyD88 on IL-1, TLR4, and IL-18 signaling but had no effect on MyD88-independent signaling pathways. Therefore, A46R and A52R are likely to represent a mechanism used by vaccinia virus of suppressing TIR domain-dependent intracellular signaling.
Molecular basis of protein kinase C-induced activation of ATP-sensitive potassium channels
Authors: Light Peter E. , Bladen Christopher , Winkfein Robert J. , Walsh Michael P. , French Robert J.
Published: July 2002

Potassium channels that are inhibited by internal ATP (K
ATP
channels) provide a critical link between metabolism and cellular excitability. Protein kinase C (PKC) acts on K
ATP
channels to regulate diverse cellular processes, including cardioprotection by ischemic preconditioning and pancreatic insulin secretion. PKC action decreases the Hill coefficient of ATP binding to cardiac K
ATP
channels, thereby increasing their open probability at physiological ATP concentrations. We show that PKC similarly regulates recombinant channels from both the pancreas and heart. Surprisingly, PKC acts via phosphorylation of a specific, conserved threonine residue (T180) in the pore-forming subunit (Kir6.2). Additional PKC consensus sites exist on both Kir and the larger sulfonylurea receptor (SUR) subunits. Nonetheless, T180 controls changes in open probability induced by direct PKC action either in the absence of, or in complex with, the accessory SUR1 (pancreatic) or SUR2A (cardiac) subunits. The high degree of conservation of this site among different K
ATP
channel isoforms suggests that this pathway may have wide significance for the physiological regulation of K
ATP
channels in various tissues and organelles.
Receptor-like kinases from
Arabidopsis
form a monophyletic gene family related to animal receptor kinases
Authors: Shiu Shin-Han , Bleecker Anthony B.
Published: July 2002

Plant receptor-like kinases (RLKs) are proteins with a predicted signal sequence, single transmembrane region, and cytoplasmic kinase domain. Receptor-like kinases belong to a large gene family with at least 610 members that represent nearly 2.5% of
Arabidopsis
protein coding genes. We have categorized members of this family into subfamilies based on both the identity of the extracellular domains and the phylogenetic relationships between the kinase domains of subfamily members. Surprisingly, this structurally defined group of genes is monophyletic with respect to kinase domains when compared with the other eukaryotic kinase families. In an extended analysis, animal receptor kinases, Raf kinases, plant RLKs, and animal receptor tyrosine kinases form a well supported group sharing a common origin within the superfamily of serine/threonine/tyrosine kinases. Among animal kinase sequences,
Drosophila
Pelle and related cytoplasmic kinases fall within the plant RLK clade, which we now define as the RLK/Pelle family. A survey of expressed sequence tag records for land plants reveals that mosses, ferns, conifers, and flowering plants have similar percentages of expressed sequence tags representing RLK/Pelle homologs, suggesting that the size of this gene family may have been close to the present-day level before the diversification of land plant lineages. The distribution pattern of four RLK subfamilies on
Arabidopsis
chromosomes indicates that the expansion of this gene family is partly a consequence of duplication and reshuffling of the
Arabidopsis
genome and of the generation of tandem repeats.
c-Jun mediates axotomy-induced dopamine neuron death
in vivo
Authors: Crocker S. J. , Lamba W. R. , Smith P. D. , Callaghan S. M. , Slack R. S. , Anisman H. , Park D. S.
Published: July 2002

Expression of the transcription factor c-Jun is induced in neurons of the central nervous system (CNS) in response to injury. Mechanical transection of the nigrostriatal pathway at the medial forebrain bundle (MFB) results in the delayed retrograde degeneration of the dopamine neurons in the substantia nigra pars compacta (SNc) and induces protracted expression and phosphorylation of c-Jun. However, the role of c-Jun after axotomy of CNS neurons is unclear. Here, we show that adenovirus-mediated expression of a dominant negative form of c-Jun (Ad.c-JunDN) inhibited axotomy-induced dopamine neuron death and attenuated phosphorylation of c-Jun in nigral neurons. Ad.c-JunDN also delayed the degeneration of dopaminergic nigral axons in the striatum after MFB axotomy. Taken together, these findings suggest that activation of c-Jun mediates the loss of dopamine neurons after axotomy injury.
Cost and conflict in animal signals and human language
Authors: Lachmann Michael , Számadó Szabolcs , Bergstrom Carl T.
Published: July 2002

The “costly signaling” hypothesis proposes that animal signals are kept honest by appropriate signal costs. We show that to the contrary, signal cost is unnecessary for honest signaling even when interests conflict. We illustrate this principle by constructing examples of cost-free signaling equilibria for the two paradigmatic signaling games of Grafen (1990) and Godfray (1991). Our findings may explain why some animal signals use cost to ensure honesty whereas others do not and suggest that empirical tests of the signaling hypothesis should focus not on equilibrium cost but, rather, on the cost of deviation from equilibrium. We use these results to apply costly signaling theory to the low-cost signals that make up human language. Recent game theoretic models have shown that several key features of language could plausibly arise and be maintained by natural selection when individuals have coincident interests. In real societies, however, individuals do not have fully coincident interests. We show that coincident interests are not a prerequisite for linguistic communication, and find that many of the results derived previously can be expected also under more realistic models of society.
Dimer formation drives the activation of the cell death protease caspase 9
Authors: Renatus Martin , Stennicke Henning R. , Scott Fiona L. , Liddington Robert C. , Salvesen Guy S.
Published: July 2002

A critical step in the induction of apoptosis is the activation of the apoptotic initiator caspase 9. We show that at its normal physiological concentration, caspase 9 is primarily an inactive monomer (zymogen), and that activity is associated with a dimeric species. At the high concentrations used for crystal formation, caspase 9 is dimeric, and the structure reveals two very different active-site conformations within each dimer. One site closely resembles the catalytically competent sites of other caspases, whereas in the second, expulsion of the “activation loop” disrupts the catalytic machinery. We propose that the inactive domain resembles monomeric caspase 9. Activation is induced by dimerization, with interactions at the dimer interface promoting reorientation of the activation loop. These observations support a model in which recruitment by Apaf-1 creates high local concentrations of caspase 9 to provide a pathway for dimer-induced activation.
The inducible
N
-acetylglucosamine catabolic pathway gene cluster in
Candida albicans
: Discrete
N
-acetylglucosamine-inducible factors interact at the promoter of
NAG1
Authors: Kumar M. Jyothi , Jamaluddin Md. S. , Natarajan K. , Kaur Deepinder , Datta Asis
Published: July 2002

The catabolic pathway of
N
-acetylglucosamine
(GlcNAc) in
Candida albicans
is an important facet of
its pathogenicity. One of the pathway genes, encoding
glucosamine-6-phosphate deaminase (
NAG1
) is
transcriptionally regulated by GlcNAc. Sequence analysis of a 4-kb
genomic clone containing
NAG1
indicates that this gene
is part of a cluster containing two other genes of the GlcNAc catabolic
pathway, i.e.,
DAC1
, GlcNAc-6-phosphate deacetylase, and
HXK1
, hexokinase. All three genes are temporally and
coordinately induced by GlcNAc suggesting a common regulatory mechanism
for these genes. The
NAG1
promoter is up-regulated when
induced by GlcNAc in
C. albicans
but not in
Saccharomyces cerevisiae. In vivo
analysis of the
deletion constructs delineated the minimal promoter to −130 bp and
mapped two regions at −200 and −400 bp upstream of +1 (ATG)
responsible for GlcNAc induction. Gel mobility-shift assays and
“footprinting” (DNase protection method) analyses revealed two
regions, 5′-GGAGCAAAAAAATGT 3′ (−164 to −150, box A) and
5′-ACGGTGAGTTG 3′ (−291 to −281, box B), that are recognized and
bound by at least two inducible activator proteins directing the
regulation of gene expression.
Combination bacteriolytic therapy for the treatment of experimental tumors
Authors: Dang Long H. , Bettegowda Chetan , Huso David L. , Kinzler Kenneth W. , Vogelstein Bert
Published: July 2002

Current chemotherapeutic approaches for cancer are in part limited
by the inability of drugs to destroy neoplastic cells within poorly
vascularized compartments of tumors. We have here systematically
assessed anaerobic bacteria for their capacity to grow expansively
within avascular compartments of transplanted tumors. Among 26
different strains tested, one (
Clostridium novyi
)
appeared particularly promising. We created a strain of
C.
novyi
devoid of its lethal toxin (
C. novyi-NT
)
and showed that intravenously injected
C. novyi-NT
spores germinated within the avascular regions of tumors in mice and
destroyed surrounding viable tumor cells. When
C.
novyi-NT
spores were administered together with conventional
chemotherapeutic drugs, extensive hemorrhagic necrosis of tumors often
developed within 24 h, resulting in significant and prolonged
antitumor effects. This strategy, called
co
mbination
ba
cterio
l
ytic
t
herapy
(COBALT), has the potential to add a new dimension to the treatment of
cancer.
PTP and LTP at a hippocampal mossy fiber-interneuron synapse
Authors: Alle Henrik , Jonas Peter , Geiger Jörg R. P.
Published: July 2002

The mossy fiber-CA3 pyramidal neuron synapse is a main
component of the hippocampal trisynaptic circuitry. Recent studies,
however, suggested that inhibitory interneurons are the major targets
of the mossy fiber system. To study the regulation of mossy
fiber-interneuron excitation, we examined unitary and compound
excitatory postsynaptic currents in dentate gyrus basket cells,
evoked by paired recording between granule and basket cells or
extracellular stimulation of mossy fiber collaterals. The application
of an associative high-frequency stimulation paradigm induced
posttetanic potentiation (PTP) followed by homosynaptic long-term
potentiation (LTP). Analysis of numbers of failures, coefficient of
variation, and paired-pulse modulation indicated that both PTP and LTP
were expressed presynaptically. The Ca
2+
chelator
1,2-bis(2-aminophenoxy)ethane-
N
,
N
,
N
′,
N
′-tetraacetic
acid (BAPTA) did not affect PTP or LTP at a concentration of 10 mM but
attenuated LTP at a concentration of 30 mM. Both forskolin, an adenylyl
cyclase activator, and phorbolester diacetate, a protein kinase C
stimulator, lead to a long-lasting increase in excitatory postsynaptic
current amplitude. H-89, a protein kinase A inhibitor, and
bisindolylmaleimide, a protein kinase C antagonist, reduced PTP,
whereas only bisindolylmaleimide reduced LTP. These results may
suggest a differential contribution of protein kinase A and C pathways
to mossy fiber-interneuron plasticity. Interneuron PTP and LTP may
provide mechanisms to maintain the balance between synaptic excitation
of interneurons and that of principal neurons in the dentate gyrus-CA3
network.
Activation of the myocyte enhancer factor-2 transcription factor by calcium/calmodulin-dependent protein kinase-stimulated binding of 14-3-3 to histone deacetylase 5
Authors: McKinsey Timothy A. , Zhang Chun Li , Olson Eric N.
Published: July 2002

Skeletal muscle differentiation is controlled by interactions
between myocyte enhancer factor-2 (MEF2) and myogenic basic
helix—loop–helix transcription factors. Association of MEF2 with
histone deacetylases (HDAC) -4 and -5 results in repression of MEF2
target genes and inhibition of myogenesis.
Calcium/calmodulin-dependent protein kinase (CaMK)
signaling promotes myogenesis by disrupting MEF2–HDAC complexes and
stimulating HDAC nuclear export. To further define the mechanisms that
confer CaMK responsiveness to HDAC4 and -5, we performed yeast
two-hybrid screens to identify HDAC-interacting factors. These screens
revealed interactions between HDAC4 and members of the 14-3-3 family of
proteins, which function as signal-dependent intracellular chaperones.
HDAC4 binds constitutively to 14-3-3 in yeast and mammalian cells,
whereas HDAC5 binding to 14-3-3 is largely dependent on CaMK signaling.
CaMK phosphorylates serines -259 and -498 in HDAC5, which subsequently
serve as docking sites for 14-3-3. Our studies suggest that 14-3-3
binding to HDAC5 is required for CaMK-dependent disruption of
MEF2–HDAC complexes and nuclear export of HDAC5, and implicate 14-3-3
as a signal-dependent regulator of muscle cell differentiation.
Crystal structure of an intracellular protease fromPyrococcus horikoshiiat 2-Å resolution
Authors: Du Xinlin , Choi In-Geol , Kim Rosalind , Wang Weiru , Jancarik Jaru , Yokota Hisao , Kim Sung-Hou
Published: July 2002

The intracellular protease fromPyrococcus horikoshii(PH1704) and PfpI fromPyrococcus furiosusare members of a class of intracellular proteases that have no sequence homology to any other known protease family. We report the crystal structure of PH1704 at 2.0-Å resolution. The protease is tentatively identified as a cysteine protease based on the presence of cysteine (residue 100) in a nucleophile elbow motif. In the crystal, PH1704 forms a hexameric ring structure, and the active sites are formed at the interfaces between three pairs of monomers.
Regular exposure to rabies virus and lack of symptomatic disease in Serengeti spotted hyenas
Authors: East Marion L. , Hofer Heribert , Cox James H. , Wulle Ulrich , Wiik Harald , Pitra Christian
Published: July 2002

We report a previously unrecognized complexity to the ecology of rabies in wildlife. Rabies-specific virus-neutralizing antibodies in spotted hyenas, the most numerous large carnivore in the Serengeti ecosystem (Tanzania, East Africa), revealed a high frequency of exposure of 37.0% to rabies virus, and reverse transcriptase (RT) PCR demonstrated rabies RNA in 13.0% of hyenas. Despite this high frequency, exposure neither caused symptomatic rabies nor decreased survival among members of hyena social groups monitored for 9 to13 years. Repeated, intermittent presence of virus in saliva of 45.5% of seropositive hyenas indicated a “carrier” state. Rabies isolates from Serengeti hyenas differed significantly (8.5% sequence divergence) from those isolated from other Serengeti carnivores, suggesting that at least two separate strains circulate within the Serengeti carnivore community. This finding is consistent with the fact that exposure in hyenas increased with age and social status, following a pattern predicted by intraspecific age and social-status-dependent oral and bite contact rates. High seroprevalence of rabies, low basic reproductive rate of the virus (R0) of 1.9, a carrier state, and the absence of symptomatic rabies in a carnivore in an ecosystem with multihost and multistrain maintenance has not been previously demonstrated for rabies. Because of the substantial differences between the hyena viral isolates and those from canids and viverrids in the Serengeti, it is unlikely that spotted hyenas were the source of rabies virus that killed several African wild dog packs in the Serengeti ecosystem in the 1990s.
Cloning and characterization of a binding subunit of the interleukin 13 receptor that is also a component of the interleukin 4 receptor.
Authors: Hilton D J , Zhang J G , Metcalf D , Alexander W S , Nicola N A , Willson T A
Published: July 2002

Interleukins 4 (IL-4) and 13 (IL-13) have been found previously to share receptor components on some cells, as revealed by receptor cross-competition studies. In the present study, the cloning is described of murine NR4, a previously unrecognized receptor identified on the basis of sequence similarity with members of the hemopoietin receptor family. mRNA encoding NR4 was found in a wide range of murine cells and tissues. By using transient expression in COS-7 cells, NR4 was found to encode the IL-13 receptor alpha chain, a low-affinity receptor capable of binding IL-13 but not IL-4 or interleukins 2, -7, -9, or -15. Stable expression of the IL-13 receptor alpha chain (NR4) in CTLL-2 cells resulted in the generation of high-affinity IL-13 receptors capable of transducing a proliferative signal in response to IL-13 and, moreover, led to competitive cross-reactivity in the binding of IL-4 and IL-13. These results suggest that the IL-13 receptor alpha chain (NR4) is the primary binding subunit of the IL-13 receptor and may also be a component of IL-4 receptors.
Ultraviolet-B photodestruction of a light-harvesting complex.
Authors: Lao K , Glazer A N
Published: July 2002

Cyanobacteria are important contributors to global photosynthesis in both marine and terrestrial environments. Quantitative data are presented on UV-B-induced damage to the major cyanobacterial photosynthetic light harvesting complex, the phycobilisome, and to each of its constituent phycobiliproteins. The photodestruction quantum yield, phi295 nm, for the phycobiliproteins is high (approximately 10(-3), as compared with approximately 10(-7) for visible light). Energy transfer on a picosecond time scale does not compete with photodestruction. Photodamage to phycobilisomes in vitro and in living cells is amplified by causing dissociation and loss of function of the complex. In photosynthetic organisms, UV-B damage to light-harvesting complexes may significantly exceed that to DNA.
The multidomain protein Trio binds the LAR transmembrane tyrosine phosphatase, contains a protein kinase domain, and has separate rac-specific and rho-specific guanine nucleotide exchange factor domains.
Authors: Debant A , Serra-Pagès C , Seipel K , O'Brien S , Tang M , Park S H , Streuli M
Published: July 2002

rho-like GTP binding proteins play an essential role in regulating cell growth and actin polymerization. These molecular switches are positively regulated by guanine nucleotide exchange factors (GEFs) that promote the exchange of GDP for GTP. Using the interaction-trap assay to identify candidate proteins that bind the cytoplasmic region of the LAR transmembrane protein tyrosine phosphatase (PT-Pase), we isolated a cDNA encoding a 2861-amino acid protein termed Trio that contains three enzyme domains: two functional GEF domains and a protein serine/threonine kinase (PSK) domain. One of the Trio GEF domains (Trio GEF-D1) has rac-specific GEF activity, while the other Trio GEF domain (Trio GEF-D2) has rho-specific activity. The C-terminal PSK domain is adjacent to an Ig-like domain and is most similar to calcium/calmodulin-dependent kinases, such as smooth muscle myosin light chain kinase which similarly contains associated Ig-like domains. Near the N terminus, Trio has four spectrin-like repeats that may play a role in intracellular targeting. Northern blot analysis indicates that Trio has a broad tissue distribution. Trio appears to be phosphorylated only on serine residues, suggesting that Trio is not a LAR substrate, but rather that it forms a complex with LAR. As the LAR PTPase localizes to the ends of focal adhesions, we propose that LAR and the Trio GEF/PSK may orchestrate cell-matrix and cytoskeletal rearrangements necessary for cell migration.
Kinetics of photo-induced electron transfer from high-potential iron-sulfur protein to the photosynthetic reaction center of the purple phototroph Rhodoferax fermentans.
Authors: Hochkoeppler A , Zannoni D , Ciurli S , Meyer T E , Cusanovich M A , Tollin G
Published: July 2002

The kinetics of photo-induced electrontransfer from high-potential iron-sulfur protein (HiPIP) to the photosynthetic reaction center (RC) of the purple phototroph Rhodoferarfermentans were studied. The rapid photooxidation of heme c-556 belonging to RC is followed, in the presence of HiPIP, by a slower reduction having a second-order rate constant of 4.8 x 10(7) M(-1) x s(-1). The limiting value of kobs at high HiPIP concentration is 95 s(-1). The amplitude of this slow process decreases with increasing HiPIP concentration. The amplitude of a faster phase, observed at 556 and 425 nm and involving heme c-556 reduction, increases proportionately. The rate constant of this fast phase, determined at 425 and 556 nm, is approximately 3 x 10(5) s(-1). This value is not dependent on HiPIP concentration, indicating that it is related to a first-order process. These observations are interpreted as evidence for the formation of a HiPIP-RC complex prior to the excitation flash, having a dissociation constant of -2.5 microM. The fast phase is absent at high ionic strength, indicating that the complex involves mainly electrostatic interactions. The ionic strength dependence of kobs for the slow phase yields a second-order rate constant at infinite ionic strength of 5.4 x 10(6) M(-1) x s(-1) and an electrostatic interaction energy of -2.1 kcal/mol (1 cal = 4.184 J). We conclude that Rhodoferar fermentans HiPIP is a very effective electron donor to the photosynthetic RC.
Complete structure of the human alpha-albumin gene, a new member of the serum albumin multigene family.
Authors: Nishio H , Dugaiczyk A
Published: July 2002

The nucleotide sequence of the human alpha-albumin gene, including 887 bp of the 5'-flanking region and 1311 bp of the 3-flanking region (24,454 in total), was determined from three overlapping lambda phage clones. The sequence spans 22,256 bp from the cap site to the polyadenylylation site, revealing a gene structure of 15 exons separated by 14 introns. The methionine initiation codon ATG is within exon 1; the termination codon TGA is within exon 14. Exon 15 is entirely untranslated and contains the polyadenylylation signal AATAAA. The deduced polypeptide chain is composed of a 21-amino-acid leader peptide, followed by 578 amino acids of the mature protein. There are seven repetitive DNA elements (Alu and Kpn) in the introns and 3-flanking region. The sizes of the 15 alpha-albumin exons match closely those of the albumin, alpha-fetoprotein, and vitamin D-binding protein genes. The exons are symmetrically placed within the three domains of the individual proteins, and they share a characteristic codon splitting pattern that is conserved among members of the gene family. The results provide strong evidence that alpha-albumin belongs to, and most likely completes with, the serum albumin gene family. Based on structural similarity, alpha-albumin appears to be most closely related to alpha-fetoprotein. The complete structure of this family of four tandemly linked genes provides a well-characterized approximately 200 kb locus in the 4q subcentromeric region of the human genome.
CAX1, an H+/Ca2+ antiporter from Arabidopsis.
Authors: Hirschi K D , Zhen R G , Cunningham K W , Rea P A , Fink G R
Published: July 2002

Reestablishment of the resting state after stimulus-coupled elevations of cytosolic-free Ca2+ requires the rapid removal of Ca2+ from the cytosol of plant cells. Here we describe the isolation of two genes, CAX1 and CAX2, from Arabidopsis thaliana that suppress a mutant of Saccharomyces cerevisiae that has a defect in vacuolar Ca2+ accumulation. Both genes encode polypeptides showing sequence similarities to microbial H+/Ca2+ antiporters. Experiments on vacuolar membrane-enriched vesicles isolated from yeast expressing CAX1 or CAX2 demonstrate that these genes encode high efficiency and low efficiency H+/Ca2+ exchangers, respectively. The properties of the CAX1 gene product indicate that it is the high capacity transporter responsible for maintaining low cytosolic-free Ca2+ concentrations in plant cells by catalyzing pH gradient-energized vacuolar Ca2+ accumulation.
General and specific brain regions involved in encoding and retrieval of events: what, where, and when.
Authors: Nyberg L , McIntosh A R , Cabeza R , Habib R , Houle S , Tulving E
Published: July 2002

Remembering an event involves not only what happened, but also where and when it occurred. We measured regional cerebral blood flow by positron emission tomography during initial encoding and subsequent retrieval of item, location, and time information. Multivariate image analysis showed that left frontal brain regions were always activated during encoding, and right superior frontal regions were always activated at retrieval. Pairwise image subtraction analyses revealed information-specific activations at (i) encoding, item information in left hippocampal, location information in right parietal, and time information in left fusiform regions; and (ii) retrieval, item in right inferior frontal and temporal, location in left frontal, and time in anterior cingulate cortices. These results point to the existence of general encoding and retrieval networks of episodic memory whose operations are augmented by unique brain areas recruited for processing specific aspects of remembered events.
Genetically engineered poxviruses for recombinant gene expression, vaccination, and safety.
Authors: Moss B
Published: July 2002

Vaccinia virus, no longer required for immunization against smallpox, now serves as a unique vector for expressing genes within the cytoplasm of mammalian cells. As a research tool, recombinant vaccinia viruses are used to synthesize and analyze the structure-function relationships of proteins, determine the targets of humoral and cell-mediated immunity, and investigate the types of immune response needed for protection against specific infectious diseases and cancer. The vaccine potential of recombinant vaccinia virus has been realized in the form of an effective oral wild-life rabies vaccine, although no product for humans has been licensed. A genetically altered vaccinia virus that is unable to replicate in mammalian cells and produces diminished cytopathic effects retains the capacity for high-level gene expression and immunogenicity while promising exceptional safety for laboratory workers and potential vaccine recipients.
Association of RNase mitochondrial RNA processing enzyme with ribonuclease P in higher ordered structures in the nucleolus: a possible coordinate role in ribosome biogenesis.
Authors: Lee B , Matera A G , Ward D C , Craft J
Published: July 2002

RNase mitochondrial RNA processing enzyme (MRP) is a nucleolar ribonucleoprotein particle that participates in 5.8S ribosomal RNA maturation in eukaryotes. This enzyme shares a polypeptide and an RNA structural motif with ribonuclease P (RNase P), a nuclear endoribonuclease originally described in the nucleus that processes RNA transcripts to generate their mature 5' termini. Both enzymes are also located in mitochondria. This report further characterizes the relationship between RNase MRP and RNase P. Antisense affinity selection with biotinylated 2'-O-methyl oligoribonucleotides and glycerol gradient fractionation experiments demonstrated that small subpopulations of RNase MRP and RNase P associate with each other in vivo in macromolecular complex, possibly 60-80S preribosomes. This latter notion was supported by fluorescence in situ hybridization experiments with antisense oligonucleotides that localized that RNA components of RNase MRP and RNase P to the nucleolus and to discrete cytoplasmic structures. These findings suggest that small subpopulations of RNase MRP and RNase P are physically associated, and that both may function in ribosomal RNA maturation or ribosome assembly.
Detecting the conformational change of transmembrane signaling in a bacterial chemoreceptor by measuring effects on disulfide cross-linking in vivo.
Authors: Hughson A G , Hazelbauer G L
Published: July 2002

Transmembrane signaling by bacterial chemoreceptors is thought to involve relative movement among the four transmembrane helices of the homodimer. We assayed that movement by measuring effects of ligand occupancy on rates of oxidative cross-linking between cysteines introduced into neighboring helices of the transmembrane domain of chemoreceptor Trg from Escherichia coli. Measurements were done on chemoreceptors in their native environment, intact cells that were motile and chemotactically responsive. Receptor occupancy did not appear to cause drastic rearrangement of the four-helix structure since, among 67 cysteine pairs tested, the same 19 exhibited oxidative cross-linking in the presence or absence of saturating chemoattractant. However, occupancy did cause subtle changes that were detected as effects on rates of cross-linking. Among the seven disulfides appropriate for measurements of initial rates of formation, ligand occupancy had significant and different effects on all three cross-links that connected the two helices within a subunit but had minimal effects on the four that spanned the packing interface between subunits. This constitutes direct evidence that the conformational change of transmembrane signaling involves significant movement within a subunit and minimal movement between subunits, a pattern deduced from several previous studies and now documented directly. Among possible modes of movement between the two helices of a subunit, axial sliding of one helix relative to the other was the conformational change that best accounted for the observed effects on cross-linking.
Polyadenylylated nuclear RNA encoded by Kaposi sarcoma-associated herpesvirus.
Authors: Sun R , Lin S F , Gradoville L , Miller G
Published: July 2002

A newly recognized gamma herpesvirus known as Kaposi sarcoma-associated herpesvirus (KSHV) or human herpesvirus 8 (HHV8) is present in Kaposi sarcomas and body-cavity-based lymphomas. Here we identify a novel abundant 1.2-kb RNA, polyadenylated nuclear RNA (PAN RNA), encoded by the virus. The majority of cDNAs produced from poly(A)-selected RNA isolated from a human body cavity lymphoma cell line 48 hr after butyrate induction of KSHV lytic replication represented PAN RNA. Within PAN RNA were two 9 and 16 nt stretches with 89% and 94% identity to U1 RNA. A third stretch of 14 nt was 93% complementary to U1. The 5' upstream region of PAN RNA contained both proximal and distal sequence elements characteristic of regulatory regions of U snRNAs, whereas the 3' end was polyadenylylated. PAN RNA was transcribed by RNA polymerase II, lacked a trimethylguanosine cap, and did not associate with polyribosomes. PAN RNA formed a speckled pattern in the nucleus typical of U snRNAs and colocalized with Sm protein. Therefore, PAN represents a new type of RNA, possessing features of both U snRNA and mRNA.