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PubMed2006

Genomic anatomy of the Tyrp1 (brown) deletion complex.

Chromosome deletions in the mouse have proven invaluable in the dissection of gene function. The brown deletion complex comprises >28 independent genome rearrangements, which have been used to identify several functional loci on chromosome 4 required for normal embryonic and postnatal development. We have constructed a 172-bacterial artificial chromosome contig that spans this 22-megabase (Mb) interval and have produced a contiguous, finished, and manually annotated sequence from these clones. The deletion complex is strikingly gene-poor, containing only 52 protein-coding genes (of which only 39 are supported by human homologues) and has several further notable genomic features, including several segments of >1 Mb, apparently devoid of a coding sequence. We have used sequence polymorphisms to finely map the deletion breakpoints and identify strong candidate genes for the known phenotypes that map to this region, including three lethal loci (l4Rn1, l4Rn2, and l4Rn3) and the fitness mutant brown-associated fitness (baf). We have also characterized misexpression of the basonuclin homologue, Bnc2, associated with the inversion-mediated coat color mutant white-based brown (B(w)). This study provides a molecular insight into the basis of several characterized mouse mutants, which will allow further dissection of this region by targeted or chemical mutagenesis.

Animals↗

PubMed1994

Activated Ki-Ras complements erythropoietin signaling in CTLL-2 cells, inducing tyrosine phosphorylation of a 160-kDa protein.

We have previously shown that expression of erythropoietin (EPO) receptor (EPOR) alone failed to confer EPO responsiveness on the interleukin 2-dependent T-cell line CTLL-2, whereas the introduction of the EPOR into interleukin 3-dependent pro-B-cell lines, such as BAF-B03, allowed the cells to proliferate in response to EPO. Here, we report that additional expression of v-Ki-Ras conferred EPO-dependent growth on CTLL-2 cells expressing the EPOR, with additional formation of a high-affinity EPOR. To investigate possible mechanisms of EPOR downstream signaling induced by v-Ki-Ras expression in these CTLL-2-derived cells, we carried out anti-phosphotyrosine immunoblot analysis of the EPOR complex immunoprecipitated with anti-EPOR antibody from lysates of cells with and without cytokine stimulation, revealing two 160-kDa and 130-kDa phosphotyrosyl proteins. An anti-JAK2 antibody did not react with these proteins, suggesting that they may represent cellular components involved in an EPO-EPOR signaling pathway induced by v-Ki-Ras. Similar phosphotyrosyl proteins were present among Friend erythroleukemia cell lines, in which the Friend virus gp55/EPOR complex on the cell surface constitutively sends signals for cell growth.

Cell Division↗

PubMed1994

Proliferative responses and binding properties of hematopoietic cells transfected with low-affinity receptors for leukemia inhibitory factor, oncostatin M, and ciliary neurotrophic factor.

Specific low-affinity receptors for leukemia inhibitory factor (LIF), oncostatin M (OSM; gp130), and ciliary neurotrophic factor (CNTF; receptor alpha, CNTFR alpha) may be utilized in various combinations to generate high-affinity binding sites and signal transduction. We have tested the ability of combinations of these receptors to transduce a proliferative signal in BAF-B03 cells. Coexpression of the LIF receptor and gp130 in these cells conferred high-affinity LIF and OSM binding and responsiveness to LIF and OSM. These cells also responded to CNTF in the absence of detectable binding. The further addition of CNTFR alpha conferred high-affinity CNTF binding and enhanced responsiveness to CNTF but did not modify responses to LIF or OSM. Coexpression of LIF receptor and CNTFR alpha resulted in a nonfunctional high-affinity binding site. These data are consistent with a role for the CNTFR alpha in enhancing CNTF action but the CNTFR alpha is not absolutely required for CNTF action and suggest a wider range of targets for CNTF.

Animals↗

PubMed1997

Pivotal role for the NFIL3/E4BP4 transcription factor in interleukin 3-mediated survival of pro-B lymphocytes.

The E2A-HLF (hepatic leukemia factor) oncoprotein, generated in pro-B lymphocytes by fusion of the trans-activation domain of E2A to the basic region/leucine zipper (bZIP) domain of HLF, functions as an anti-apoptotic transcription factor in leukemic cell transformation. When introduced into interleukin 3 (IL-3)-dependent mouse pro-B lymphocytes, E2A-HLF prevents apoptosis induced by growth factor deprivation, suggesting that IL-3 mediates cell survival through activation of a transcription factor whose activity can be constitutively replaced by the chimeric oncoprotein. We considered four bZIP transcription factors as candidates for this putative IL-3-regulated factor, each of which binds avidly to the DNA consensus sequence recognized by E2A-HLF and is related to the Caenorhabditis elegans CES-2 (cell death specification protein) neuron-specific mediator of cell death. The expression and binding activity of the Nfil3 protein (also called E4bp4), but not of Hlf, Dbp, or Tef, was found to be regulated by IL-3 in mouse pro-B cell lines (Baf-3 and FL5.12). Northern blot analysis showed that Nfil3/E4bp4 is regulated as a "delayed-early" IL-3-responsive gene, requiring de novo protein synthesis. In the absence of IL-3, enforced expression of the human NFIL3/E4BP4 cDNA promoted the survival but not the growth of IL-3-dependent pro-B cells. Our results implicate NFIL3/E4BP4 (nuclear factor regulated by IL-3/adenovirus E4 promoter binding protein) in a distinct growth factor-regulated signaling pathway that is responsible for the survival of early B-cell progenitors, and whose alteration by E2A-HLF leads to childhood B lineage leukemia.

Adenovirus E4 Proteins↗

PubMed1998

Architectural DNA binding by a high-mobility-group/kinesin-like subunit in mammalian SWI/SNF-related complexes.

The SWI/SNF complex in yeast and Drosophila is thought to facilitate transcriptional activation of specific genes by antagonizing chromatin-mediated transcriptional repression. The mechanism by which it is targeted to specific genes is poorly understood and may involve direct DNA binding and/or interactions with specific or general transcription factors. We have previously purified a mammalian complex by using antibodies against BRG1, a human homologue of SWI2/SNF2. This complex is likely functionally related to the yeast SWI/SNF complex because all five subunit identified so far (referred to as BAFs, for BRG1-associated factors) are homologues of the yeast SWI/SNF subunits. However, we now describe the cloning of the 57-kDa subunit (BAF57), which is present only in higher eukaryotes but not in yeast. BAF57 is shared by all mammalian complexes and contains a high-mobility-group (HMG) domain adjacent to a kinesin-like region. Both recombinant BAF57 and the whole complex bind four-way junction (4WJ) DNA, which is thought to mimic the topology of DNA as it enters or exits the nucleosome. Surprisingly, complexes with mutations in the HMG domain of BAF57 can still bind 4WJ DNA and mediate ATP-dependent nucleosome disruption. Our work describes the first DNA binding subunit for SWI/SNF-like complexes and suggest that the mechanism by which mammalian and Drosophila SWI/SNF-like complexes interact with chromatin may involve recognition of higher-order chromatin structure by two or more DNA binding domains.

Amino Acid Sequence↗

PubMed1999

Targeting a SWI/SNF-related chromatin remodeling complex to the beta-globin promoter in erythroid cells.

Chromatin remodeling complexes such as the SWI/SNF complex make DNA accessible to transcription factors by disrupting nucleosomes. However, it is not known how such complexes are targeted to the promoter. For example, a SWI/SNF1-like chromatin remodeling complex erythroid Krüppel-like factor (EKLF) coactivator-remodeling complex 1 (E-RC1) disrupts the nucleosomes over the human beta-globin promoter in an EKLF-dependent manner. However, it is not known whether E-RC1 is targeted specifically to the beta-globin promoter or whether E-RC1 is randomly targeted, but its activity is evident only at the beta-globin promoter. Because E-RC1 cannot remodel chromatin over the beta-globin promoter without EKLF in vitro, it has been proposed that SWI/SNF1-like complexes such as E-RC1 are targeted specifically to the promoter by selectively interacting with promoter-associated transcription factors such as EKLF. In this report, we test this hypothesis in the cellular context by using the ProteIN POsition Identification with Nuclease Tail (PIN*POINT) assay. We find that the Brahma-related gene (BRG) 1 and BRG1-associated factor (BAF) 170 subunits of E-RC1 are both recruited near the transcription initiation site of the beta-globin promoter. On transiently transfected templates, both the locus control region and the EKLF-binding site are important for their recruitment to the beta-globin promoter in mouse erythroleukemia cells. When the beta-globin promoter was linked to the cytomegalovirus enhancer, the E-RC1 complex was not recruited, suggesting that recruitment of the E-RC1 complex is not a general property of enhancers.

Base Sequence↗

PubMed1995

Interleukin-3, erythropoietin, and prolactin activate a STAT5-like factor in lymphoid cells.

Interleukin-3 (IL-3)-, erythropoietin (EPO)-, and prolactin (PRL)-induced signal transduction via the JAK/STAT pathway was studied in the IL-3-dependent BAF-3 lymphoid cell line. Transfected cells expressing either the long form of the PRL receptor or the EPO receptor were used. We demonstrated that IL-3, EPO, and PRL activated a transcription factor related to the mammary transcription factor STAT5 but not to STAT1, -2, -3, or -4 as opposed to interferon gamma (IFN gamma) which activated STAT1 in the same cells. Similarly, PRL and EPO activated a STAT5-like factor (STAT5-L) in the rat Nb2 and the human UT7 cells expressing endogenous PRL and EPO receptors, respectively. The hematopoietic STAT5-L activated by IL-3, EPO, or PRL was identified as a 97-kDa tyrosine-phosphorylated protein. These results confer to STAT5 a much broader role than previously suggested.

Animals↗

PubMed2000

Growth hormone (GH)-independent dimerization of GH receptor by a leucine zipper results in constitutive activation.

Growth hormone initiates signaling by inducing homodimerization of two GH receptors. Here, we have sought to determine whether constitutively active receptor can be created in the absence of the extracellular domain by substituting it with high affinity leucine zippers to create dimers of the growth hormone receptor (GHR) signaling domain. The entire extracellular domain of the GHR was replaced by the hemagglutinin-tagged zipper sequence of either the c-Fos or c-Jun transcription factor (termed Fos-GHR and Jun-GHR, respectively). Transient transfection of Fos-GHR or Jun-GHR resulted in activation of the serine protease inhibitor 2.1 promoter in Chinese hamster ovary-K1 cells to a level equal to that achieved by fully activated wild type GHR. Furthermore, stable expression of Jun-GHR alone or Fos-GHR and Jun-GHR together in the interleukin 3-dependent BaF-B03 cell line resulted in cell proliferation after interleukin 3 withdrawal at a rate equal to maximally stimulated wild type GHR-expressing cells. Activation of STAT 5b was also observed in Fos-Jun-GHR-expressing cells at a level equal to that in chronically GH-treated GHR-expressing cells. Thus, forced dimerization of the transmembrane and cytoplasmic domains of the GHR in the absence of the extracellular domain can lead to the constitutive activation of known GH signaling end points, supporting the view that proximity of Janus kinase 2 (JAK2) kinases is the essential element in signaling. Such constitutively active GH receptors may have particular utility for transgenic livestock applications.

Amino Acid Sequence↗

PubMed2000

Point mutants of c-raf-1 RBD with elevated binding to v-Ha-Ras.

A mutational analysis of the Ras-binding domain (RBD) of c-Raf-1 identified three amino acid positions (Asn(64), Ala(85), and Val(88)) where amino acid substitution with basic residues increases the binding of RBD to recombinant v-Ha-Ras. The greatest increase in binding (6-9-fold) was observed with the A85K-RBD mutant. The elevated binding for the A85K-RBD and V88R-RBD mutants was also detected with Ras expressed in cultured mammalian cells, namely NIH-3T3 and BAF cells. None of the wild type residues in RBD positions Asn(64), Ala(85), and Val(88) have been previously implicated in the interaction with Ras (Block, C., Janknecht, R., Herrmann, C., Nassar, N., and Wittinghofer, A. (1996) Nat. Struct. Biol. 3, 244-251; Nassar, N., Horn, G., Herrmann, C., Scherer, A., McCormick, F., and Wittinghofer, A. (1995) Nature 375, 554-560). The discovery of elevated binding among the mutants in these positions implies that additional RBD residues can be used to generate the Ras. RBD complex. These findings are of particular significance in the design of Ras antagonists based on the RBD prototype. The A85K-RBD mutant can be used to develop an assay for measuring the level of activated Ras in cultured cells; Sepharose-linked A85K-RBD.GST fusion protein served as an activation-specific probe to precipitate Ras.GTP but not Ras.GDP from epidermal growth factor-stimulated cells. A85K-RBD precipitates up to 5-fold more Ras.GTP from mammalian cells than wild type RBD.

Amino Acid Sequence↗

PubMed2002

REST repression of neuronal genes requires components of the hSWI.SNF complex.

A function of the transcription factor REST is to block the expression of neuronal phenotypic traits in non-neuronal cells. Previous studies have shown that REST-mediated repression requires histone deacetylase activity and that recruitment of deacetylases is mediated by two co-repressors, Sin3A and CoREST. In this study, we show that a repressor domain in CoREST interacts with BRG1-associated factor (BAF) 57, a component of the hSWI.SNF complex. In vivo, BAF57 occupies the neuronal sodium channel gene (Nav1.2) promoter, and targeting to this gene requires REST. In addition to BAF57, the ATPase BRG1 and BAF170, other members of the hSWI.SNF complex, are also present in the REST.CoREST repressor complex. Microinjection of specific antibodies against BRG1, BAF57, or BAF170 into Rat1 fibroblasts relieves repression of RE1 reporter genes. Together, our data suggest that ATP-dependent chromatin remodeling, as well as histone deacetylation, is needed for REST-mediated repression.

Alternative Splicing↗

PubMed2026

A CRISPR-Cas9 screen identifies LAPTM4A (lysosomal protein transmembrane 4 alpha) as a key host barrier against PRRSV infection.

Porcine reproductive and respiratory syndrome virus (PRRSV) manipulates host intracellular processes, particularly macroautophagy/autophagy and lysosomal function, to facilitate its replication and spread. However, the precise host factors and molecular mechanisms by which PRRSV remodels the autophagy-lysosome axis remain poorly defined. Here, we performed a CRISPR-Cas9 knockout screen targeting 1,332 genes involved in protein degradation, metabolism, and vesicular trafficking, and identified LAPTM4A (lysosomal protein transmembrane 4 alpha) as a critical antiviral factor involved in the lysosomal pathway. A yeast two-hybrid screen identified LAPTM4A as an interactor of PRRSV GP5 (glycoprotein 5). Mechanistically, GP5 recruits the E3 ubiquitin ligase NEDD4 and the autophagy receptor SQSTM1/p62 to promote K63-linked polyubiquitination of LAPTM4A, leading to its autophagic degradation. This selective degradation activates the AMPK-ULK1-MAP1LC3/LC3 signaling cascade, initiating autophagy while facilitating MTOR-lysosome colocalization, thereby suppressing TFEB nuclear translocation and transcription of lysosome-related genes. The resulting incomplete autophagic flux enhances viral replication. Additionally, in terms of host defense, LAPTM4A maintains lysosomal homeostasis by restraining excessive autophagy through AMPK-ULK1-LC3 signaling and promoting TFEB-dependent lysosomal gene expression by impairing the binding of RPTOR/raptor to MTOR, thus providing broad antiviral protection against multiple RNA viruses. Collectively, our findings identify LAPTM4A as a central regulator of lysosome-autophagy homeostasis and reveal a viral strategy that dismantles this defense axis to facilitate infection.Abbreviations: ATG5: autophagy related 5; AMPK: adenosine 5'-monophosphate (AMP)-activated protein kinase; Baf A1: bafilomycin A1; CHX: cycloheximide; Co-IP: co-immunoprecipitation; DMVT library: protein degradation, metabolism, and vesicular trafficking library; LAPTM4A: lysosomal protein transmembrane 4 alpha; MAGeCK: model-based analysis of genome-wide CRISPR-Cas9 knockout; MOI: multiplicity of infection; MTOR: mechanistic target of rapamycin kinase; NC: negative control; PAMs: porcine alveolar macrophages; PRKAA/AMPKα: protein kinase AMP-activated catalytic subunit alpha; PRRSV: porcine reproductive and respiratory syndrome virus; qRT-PCR: quantitative real-time PCR; siRNA: small interfering RNA; SQSTM1/p62: sequestosome 1; TCID50: 50% tissue culture infective dose; TFEB: transcription factor EB; Ub: ubiquitin; ULK1: unc-51 like autophagy activating kinase 1; WT: wild type.

Animals↗

PubMed1994

Molecular genetics of the brown (b)-locus region of mouse chromosome 4. II. Complementation analyses of lethal brown deletions.

Numerous new mutations at the brown (b) locus in mouse chromosome 4 have been recovered over the years in germ-cell mutagenesis experiments performed at the Oak Ridge National Laboratory. A large series of radiation- and chemical-induced b mutations known to be chromosomal deletions, and also known to be prenatally lethal when homozygous, were analyzed by pairwise complementation crosses as well as by pseudodominance tests involving flanking loci defined by externally visible phenotypes. These crosses were designed to determine the extent of each deletion on the genetic and phenotype map of the chromosomal region surrounding the b locus; the crosses also provided basic data that assigned deletions to complementation groups and defined four new loci associated with aberrancies in normal development. Specifically, the pseudodominance tests identified deletions that include the proximally mapping whirler (wi) and the distally mapping depilated (dep) genes, thereby bracketing these loci defined by visible developmental abnormalities with landmarks (deletion breakpoints) that are easily identified on the physical map. Furthermore, the complementation crosses, which were supplemented with additional crosses that allowed determination of the gross time of lethality of selected deletions, defined four new loci required for normal development. Homozygous deletion of one of these loci (b-associated fitness, baf) results in a runting syndrome evident during postnatal development; deletion of one locus [l(4)2Rn] causes death in the late gestation/neonatal period; and deletion of either of two loci [l(4)1Rn or l(4)3Rn] results in embryonic death, most likely in pre-, peri- or postimplantation stages. The placement of these new functionally defined loci on the evolving molecular map of the b region should be useful for continuing the analysis of the roles played in development by genes in this segment of chromosome 4.

Animals↗

PubMed2001

Chloroquine-induced neuronal cell death is p53 and Bcl-2 family-dependent but caspase-independent.

Chloroquine is a lysosomotropic agent that causes marked changes in intracellular protein processing and trafficking and extensive autophagic vacuole formation. Chloroquine may be cytotoxic and has been used as a model of lysosomal-dependent cell death. Recent studies indicate that autophagic cell death may involve Bcl-2 family members and share some features with caspase-dependent apoptotic death. To determine the molecular pathway of chloroquine-induced neuronal cell death, we examined the effects of chloroquine on primary telencephalic neuronal cultures derived from mice with targeted gene disruptions in p53, and various caspase and bcl-2 family members. In wild-type neurons, chloroquine produced concentration- and time-dependent accumulation of autophagosomes, caspase-3 activation, and cell death. Cell death was inhibited by 3-methyladenine, an inhibitor of autophagic vacuole formation, but not by Boc-Asp-FMK (BAF), a broad caspase inhibitor. Targeted gene disruptions of p53 and bax inhibited and bcl-x potentiated chloroquine-induced neuron death. Caspase-9- and caspase-3-deficient neurons were not protected from chloroquine cytotoxicity. These studies indicate that chloroquine activates a regulated cell death pathway that partially overlaps with the apoptotic cascade.

Amebicides↗

PubMed2001

Insulin-like growth factor-I and over-expression of Bcl-xL prevent glucose-mediated apoptosis in Schwann cells.

Schwann cells (SCs), the myelinating cells of the peripheral nervous system, are lost or damaged in patients suffering from diabetic neuropathy. In the current study, 2 model systems are used to study the mechanism of SC damage in diabetic neuropathy: the streptozotocin (STZ)-treated diabetic rat and cultures of purified SCs in vitro. Electron microscopy of dorsal root ganglia from STZ-treated rats reveals classic ultrastructural features of apoptosis in SCs, including chromatin clumping and prominent vacuolation. Bisbenzamide staining of SCs cultured in hyperglycemic defined media shows nuclear blebbing of apoptotic cells. Insulin-like growth factor-I (IGF-I) is protective. LY294002, a phosphatidylinositol 3-kinase (PI 3-kinase) inhibitor, blocks the effect of IGF-I. High glucose induces caspase cleavage in apoptotic SCs--an effect that is blocked by bok-asp-fmk (BAF), a caspase inhibitor. Although Bcl-xL expression remains unchanged in experimental conditions, over-expression of Bcl-xL protects SCs from apoptosis. In summary, hyperglycemia induces caspase activation and morphologic changes in SCs consistent with apoptotic death, both in vivo and in vitro. Over-expression of Bcl-xL, or IGF-I, signaling via PI 3-kinase, protects SCs from glucose-mediated apoptosis in vitro. IGF-I may be useful in preventing hyperglycemia-induced damage to SCs in patients suffering from diabetic neuropathy.

Animals↗

PubMed2025

CNV-Finder: Streamlining Copy Number Variation Discovery.

Copy Number Variations (CNVs) play pivotal roles in the etiology of complex diseases and are variable across diverse populations. Understanding the association between CNVs and disease susceptibility is significant in disease genetics research and often requires analysis of large sample sizes. One of the most cost-effective and scalable methods for detecting CNVs is based on normalized signal intensity values, such as Log R Ratio (LRR) and B Allele Frequency (BAF), from Illumina genotyping arrays. In this study, we present CNV-Finder, a novel pipeline integrating deep learning techniques on array data, specifically a Long Short-Term Memory (LSTM) network, to expedite the large-scale identification of CNVs within predefined genomic regions. This facilitates efficient prioritization of samples for time-consuming or costly subsequent analyses such as Multiplex Ligation-dependent Probe Amplification (MLPA), short-read, and long-read whole genome sequencing. We incorporate four genes to establish our methods-Parkin (PRKN), Leucine Rich Repeat And Ig Domain Containing 2 (LINGO2), Microtubule Associated Protein Tau (MAPT), and alpha-Synuclein (SNCA)-which may be relevant to neurological diseases such as Alzheimer's disease (AD), Parkinson's disease (PD), Progressive Supranuclear Palsy (PSP), or related disorders such as essential tremor (ET). By training our models on expert-annotated samples and validating them across diverse cohorts, including those from the Global Parkinson's Genetics Program (GP2) and additional dementia-specific databases, we demonstrate the efficacy of CNV-Finder in accurately detecting deletions and duplications. Our pipeline outputs app-compatible files for visualization within CNV-Finder's interactive web application. This interface enables researchers to review predictions and filter displayed samples by model prediction values, LRR range, and variant count in order to explore or confirm results. Our pipeline integrates this human feedback to enhance model performance and reduce false positive rates. Through a series of comprehensive analyses and validations using visual inspection, MLPA, short-read, and long-read sequencing data, we demonstrate the robustness and adaptability of CNV-Finder in identifying CNVs with regions of varied size, probe density, and noise. Our findings highlight the significance of contextual understanding and human expertise in enhancing the precision of CNV identification, particularly in complex genomic regions like 17q21.31. The CNV-Finder pipeline is a scalable, publicly available resource for the scientific community, available on GitHub (https://github.com/GP2code/CNV-Finder; DOI 10.5281/zenodo.14182563). CNV-Finder not only expedites accurate candidate identification but also significantly reduces the manual workload for researchers, enabling future targeted validation and downstream analyses in regions or phenotypes of interest.

Copy Number Variation (CNV)↗

PubMed1996

Diversity and specialization of mammalian SWI/SNF complexes.

The SWI/SNF complex in yeast facilitates the function of transcriptional activators by opposing chromatin-dependent repression of transcription. We demonstrate that in mammals SWI/SNF complexes are present in multiple forms made up of 9-12 proteins that we refer to as BRG1-associated factors (BAFs) ranging from 47 to 250 kD. We have isolated cDNAs for human BAF155, BAF170, and BAF60. BAF155 and BAF170 are encoded by separate genes that are both homologs of yeast SWI3. Both contain a region of similarity to the DNA binding domain of myb, but lack the basic residues known to be necessary for interaction with DNA. The two SWI3 homologs copurify on antibody columns specific for either BAF155 or BAF170, indicating that they are in the same complex. BAF60 is encoded by a novel gene family. An open reading frame from yeast, which is highly homologous, encodes the previously uncharacterized 73-kD subunit of the yeast SWI/SNF complex required for transcriptional activation by the glucocorticoid receptor (Cairns et al., this issue). BAF60a is expressed in all tissues examined, whereas BAF60b and BAF60c are expressed preferentially in muscle and pancreas, respectively. BAF60a is present within the 2000-kD BRG1 complex, whereas BAF60b is in a distinct complex that shares some but not all subunits with the BRG1 complex. The observed similarity between mammalian BAF190, BAF170, BAF155, BAF60, and BAF47 and yeast SNF2/SWI2, SWI3, SWI3, SWP73, and SNF5, respectively, underscores the similarity of the mammalian and yeast complexes. However, the complexes in mammals are more diverse than the SWI/SNF complex in yeast and are likely dedicated to developmentally distinct functions.

Amino Acid Sequence↗

PubMed2003

Effects of pressure on the fragile nature of fluorozirconates studied by molecular dynamics simulations.

Molecular dynamics simulations for a multicomponent zirconium fluoride, ZBEN (55ZrF(4)-17BaF(2)-5EuF(3)-23NaF) have been carried out at various temperatures and pressures including those of the molten and glassy states. The effect of pressure on the fragile nature of ZBEN was investigated. The relaxation times were calculated from the decay curves of the intermediate scattering function. The fragile nature of ZBEN was reflected by the obvious non-Arrhenius behavior in the temperature dependence of the relaxation time. The so-called "Angell plot" of the relaxation time was represented by a single curve irrespective of applied pressure; the fragile nature changes negligibly with pressure. This seems to contradict the enhancement of the connectivity of ZrF(n) polyhedra under high pressure. The origin of the pressure effects is discussed in comparison with those for molecular liquids and covalent-network glasses.

Journal Article↗

PubMed2001

Neutron capture on (180)Ta(m): clue for an s-process origin of nature's rarest isotope.

The neutron capture cross section of (180)Ta(m) has been measured in the keV range, yielding a stellar average of 1465+/-100 mb at kT = 30 keV. Though the sample contained only 6.7 mg (180)Ta(m) (at an enrichment of 5.5%), the few capture events could be separated from much larger backgrounds by a unique combination of high efficiency, good energy resolution, and high granularity of the Karlsruhe 4 pi BaF(2) detector. A detailed s-process analysis based on this first experimental value indicates that (180)Ta(m) is predominantly of s-process origin.

Journal Article↗