Showing papers on "Histone H4 published in 1995"
TL;DR: In this paper, the analogous residues, lysines 5 and 12, are shown to be acetylated in Drosophila and HeLa H4, but no evidence has been obtained for acetylation of newly synthesized H3 in HeLa cells.
Abstract: Newly synthesized histone H4 is deposited in a diacetylated isoform in a wide variety of organisms. In Tetrahymena a specific pair of residues, lysines 4 and 11, have been shown to undergo this modification in vivo. In this report, we demonstrate that the analogous residues, lysines 5 and 12, are acetylated in Drosophila and HeLa H4. These data strongly suggest that deposition-related acetylation sites in H4 have been highly, perhaps absolutely, conserved. In Tetrahymena and Drosophila newly synthesized histone H3 is also deposited in several modified forms. Using pulse-labeled H3 we have determined that, like H4, a specific, but distinct, subset of lysines is acetylated in these organisms. In Tetrahymena, lysines 9 and 14 are highly preferred sites of acetylation in new H3 while in Drosophila, lysines 14 and 23 are strongly preferred. No evidence has been obtained for acetylation of newly synthesized H3 in HeLa cells. Thus, although the pattern and sites of deposition-related acetylation appear to be highly conserved in H4, the same does not appear to be the case for histone H3.
513 citations
TL;DR: The H AT1 protein expressed in Escherichia coli gave histone acetyltransferase activity in vitro, demonstrating that HAT1 is the structural gene for the enzyme.
363 citations
TL;DR: It is concluded that nucleosomes containing acetylated H4 are scattered infrequently and possibly randomly through coding and adjacent regions and are essentially absent from heterochromatin.
Abstract: By immunoprecipitation of chromatin fragments from cultured human HL-60 cells with antibodies specific for H4 acetylated at specific lysine residues we have defined the level of H4 acetylation within transcriptionally active and inactive regions of the genome. H4 within or adjacent to coding regions had a similar level of overall acetylation to input (bulk) chromatin and a similar pattern of acetylation of individual lysines (i.e. 16 > 8, 12 > 5). The acetylation of H4 in coding (and adjacent) regions was not correlated with transcriptional activity and did not vary with position along the constitutively active c-myc gene. Turnover of H4 acetates was not selectively increased in transcriptionally active chromatin. H4 associated with centric heterochromatin or with the CCCTAA repeat of telomeric heterochromatin was infrequently acetylated (< 1%) at all lysines. We conclude that nucleosomes containing acetylated H4 are scattered infrequently and possibly randomly through coding and adjacent regions and are essentially absent from heterochromatin. Induction of differentiation of HL-60 cells by exposure to dimethylsulfoxide or 12-o-tetradecanoylphorbol 13-acetate (TPA) did not alter the level of H4 acetylation within either the c-myc or c-fos genes or other coding regions, but did induce a transient increase in H4 acetylation within centric heterochromatin.
252 citations
TL;DR: The ability of mutations affecting the structure of the histone octamer to relieve the need for SWI and SNF products supports the proposal that the SWI/SNF complex stimulates transcription by altering chromatin structure and can account for the apparent conservation of SWI or SNF proteins in eukaryotes other than yeast.
Abstract: Transcription of many yeast genes requires the SWI/SNF regulatory complex. Prior studies show that reduced transcription of the HO gene in swi and snf mutants is partially relieved by mutations in the SIN1 and SIN2 genes. Here we show that SIN2 is identical to HHT1, one of the two genes coding for histone H3, and that mutations in either can result in a Sin- phenotype. These mutations are partially dominant to wild type and cause amino acid substitutions in three conserved positions in the structured domain of histone H3. We have also identified partially dominant sin mutations that affect two conserved positions in the histone-fold domain of histone H4. Three sin mutations affect surface residues proposed to interact with DNA and may reduce affinity of DNA for the histone octamer. Two sin mutations affect residues at or near interfaces between (H2A-H2B) dimer and (H3-H4)2 tetramer subunits of the histone octamer and may affect nucleosome stability or conformation. The ability of mutations affecting the structure of the histone octamer to relieve the need for SWI and SNF products supports the proposal that the SWI/SNF complex stimulates transcription by altering chromatin structure and can account for the apparent conservation of SWI and SNF proteins in eukaryotes other than yeast.
247 citations
TL;DR: Analysis of the activity and binding of Sp3 on several eukaryotic promoters that contain G/C boxes and are known to be regulated during cellular proliferation and the cell cycle suggests that Sp3 may contribute to the control of proliferation- and/or cell-regulated promoters depending upon the context and/ or number of functional Sp1 binding sites.
Abstract: The transcription factor Sp1 plays a key role in the activation of many cellular and viral gene promoters, including those that are regulated during the cell cycle. However, recent evidence indicates that Sp1 belongs to a larger family of factors which bind G/C box elements in order to either activate or repress transcription. Sp3, a member of this family, functions to repress transcriptional activation in two viral promoters, most likely by competing with Sp1 for GC box/Sp binding sites. However, the physiological role of Sp3 in the repression of endogenous cellular promoters has not been experimentally addressed. In the present study, we analyze the activity and binding of Sp3 on several eukaryotic promoters that contain G/C boxes and are known to be regulated during cellular proliferation and the cell cycle. Using antibodies specific for Sp1 and Sp3, we observe that both of these factors localize to the cell nucleus and have a similar, dispersed subnuclear distribution. Further, using gel mobility shift assays, we show that both Sp1 and Sp3 interact specifically with the histone H4 promoter. Transient cotransfections of Drosophila cells with Sp1 and Sp3 expression vectors and with the histone H4, thymidine kinase (TK), or dihydrofolate reductase (DHFR) promoters show that only the DHFR promoter, containing multiple functional GC boxes, displays Sp3 repression of Sp1 activation. In contrast, the single G/C boxes within the histone H4 or TK promoters, which confer transcriptional activation via Sp1 binding, are not responsive to repression by Sp3. Therefore, we demonstrate that the endogenous cellular DHFR promoter is selectively responsive to Sp3 repression. The data suggest that Sp3 may contribute to the control of proliferation- and/or cell-regulated promoters depending upon the context and/or number of functional Sp1 binding sites.
201 citations
TL;DR: The results demonstrate a link between IRF-2 and a gene that is functionally coupled to DNA replication and cell-cycle progression at the Gl/S phase transition and has oncogenic potential.
Abstract: The human histone H4 gene FO108 is regulated during the cell cycle with a peak in transcription during early S phase. The cell-cycle element (CCE) required for H4 histone activation is a sequence of 11 base pairs that binds a protein factor in electrophoretic mobility shift assays that has been designated histone nuclear factor M (HiNF-M). Here we report the purification of HiNF-M, and show it to be a protein of relative molecular mass (M(r)) 48K that is identical to interferon (IFN) regulatory factor 2 (IRF-2), a negative transcriptional regulator of the IFN response. Recombinant IRF-2 (as well as the related protein IRF-1 (ref. 5)) binds the CCE specifically and activates transcription of this H4 histone gene. IRF-2 has been shown to have oncogenic potential, and our results demonstrate a link between IRF-2 and a gene that is functionally coupled to DNA replication and cell-cycle progression at the G1/S phase transition.
189 citations
TL;DR: Results indicate that the lysine-dependent function of histone H4 is required for the maintenance of genome integrity, and that DNA damage resulting from the loss of this function activates the RAD9-dependent G2/M checkpoint pathway.
Abstract: The normal progression of Saccharomyces cerevisiae through nuclear division requires the function of the amino-terminal domain of histone H4. Mutations that delete the domain, or alter 4 conserved lysine residues within the domain, cause a marked delay during the G2 +M phases of the cell cycle. Site-directed mutagenesis of single and multiple lysine residues failed to map this phenotype to any particular site; the defect was only observed when all four lysines were mutated. Starting with a quadruple lysine-to-glutamine substitution allele, the insertion of a tripeptide containing a single extra lysine residue suppressed the G2+M cell cycle defect. Thus, the amino-terminal domain of histone H4 has novel genetic functions that depend on the presence of lysine per se, and not a specific primary peptide sequence. To determine the nature of this function, we examined H4 mutants that were also defective for G2/M checkpoint pathways. Disruption of the mitotic spindle checkpoint pathway had no effect on the phenotype of the histone amino-terminal domain mutant. However, disruption of RADg, which is part of the pathway that monitors DNA integrity, caused precocious progression of the H4 mutant through nuclear division and increased cell death. These results indicate that the lysine-dependent function of histone H4 is required for the maintenance of genome integrity, and that DNA damage resulting from the loss of this function activates the RAD9-dependent G2/M checkpoint pathway.
174 citations
TL;DR: It is concluded that, in vivo, PTH upregulates cell differentiation in trabecular bone by transient stimulation of the early response genes and IL-6, while downregulating cell proliferation.
152 citations
TL;DR: The results suggest that changes in chromatin structure underlie, at least in part, zygotic gene activation in the mouse.
Abstract: Using immunofluorescent labeling and laser-scanning confocal microscopy, we show that isoforms of histone H4 acetylated on lysine 5, 8 and/or 12 (H4.Ac5-12), as well as RNA polymerase II, become enriched at the nuclear periphery around the time of zygotic gene activation, i.e., the 2-cell stage, in the preimplantation mouse embryo. In contrast, DNA and H4 acetylated on lysine 16 are uniformly distributed throughout the cytoplasm. Culture of embryos with inhibitors of histone deacetylase trichostatin A and trapoxin results in an increase in the (1) amount of acetylated histone H4 detected by immunoblotting, (2) intensity and sharpness of the peripheral staining for H4.Ac5-12, and (3) relative rate of synthesis of proteins that are markers for zygotic gene activation. The enhanced staining for H4.Ac5-12 at the nuclear periphery seems to require DNA replication, but appears independent of cytokinesis or transcription, since its development is inhibited by aphidicolin but not by either cytochalasin D or alpha-amanitin. Lastly, the restricted localization of H4.Ac 5-12 is not observed in the 4-cell embryo or at later stages of preimplantation development. These results suggest that changes in chromatin structure underlie, at least in part, zygotic gene activation in the mouse.
124 citations
TL;DR: Results are consistent with a role for histone H4 acetylation in t-PA induction by butyrate in HUVEC, and suggest that both compounds act through a common regulatory mechanism.
Abstract: We have previously shown that the pleiotropic agent sodium butyrate strongly stimulates tissue-type plasminogen activator (t-PA) expression in human umbilical vein endothelial cells (HUVEC). Here we provide the following evidence that the butyrate-induced t-PA expression in HUVEC involves histone H4 acetylation. (1) t-PA induction by butyrate occurs at the transcriptional level and does not require new protein synthesis, indicating a direct effect. (2) t-PA induction by butyrate can be fully mimicked by a specific, structurally unrelated, histone deacetylase inhibitor, trichostatin A. (3) At optimally stimulatory conditions, a combination of butyrate and trichostatin A does not enhance t-PA production more than each of the compounds alone, indicating that both compounds act through a common regulatory mechanism. (4) Induction of t-PA transcription by butyrate and trichostatin A was found to be preceded by histone H4 acetylation; at suboptimal inducing concentrations of butyrate and trichostatin A, the degree of acetylation of histone H4 caused by each agent was similarly reduced. These results are consistent with a role for histone H4 acetylation in t-PA induction by butyrate in HUVEC.
119 citations
TL;DR: It is demonstrated that HSP70.1-associated transcription factors are not limiting, and that instead, there is a progressive maturation of chromatin structure that is directly involved in HSP 70.1 regulation during early mouse development.
Abstract: In the widely studied model organisms, Drosophila and Xenopus, early embryogenesis involves an extended series of nuclear divisions prior to activation of the zygotic genome. The mammalian embryo differs in that the early cleavage phase is already characterized by regulated cell cycles with specific zygotic gene expression. In the mouse, where major activation of the zygotic genome occurs at the 2-cell stage, the HSP70.1 gene is among the earliest genes to be expressed. We investigated the developmentally regulated expression of this gene during the preimplantation period, using a luciferase transgene, with or without flanking scaffold attachment regions (SARs). Cleavage stage-specific modifications in expression profiles were examined in terms of histone H4 acetylation status, topoisomerase II activity, and the localisation of HMG-I/Y, a nuclear protein with known affinity for the AT-tracts of SARs. We demonstrate that HSP70.1-associated transcription factors are not limiting, and that instead, there is a progressive maturation of chromatin structure that is directly involved in HSP70.1 regulation during early mouse development.
TL;DR: It is shown that while deletions of the H4 and H3 N‐termini have similar effects on dam methylase access in the GAL1 coding region, the H 4 N‐Terminal deletion uniquely alters dam access at a region near the TATA element, independent of the transcriptional state of GAL 1.
Abstract: Deletion of the histone H4 N-terminal residues 4-23 decreases activation of the GAL1 promoter as much as 20-fold, while deletion of histone H3 N-terminal residues 4-15 hyperactivates GAL1 approximately 3-fold. In an attempt to understand the mechanisms by which these two different events take place, we have examined the effects of the H4 and H3 lesions on GAL1 chromatin structure. The bacterial dam methylase, which methylates adenine residues of GATC sequences, was used as an in vivo probe for chromatin structure and both indirect end-labeling and ligation mediated PCR (LMPCR) analysis of micrococcal nuclease digestions were used to analyze chromatin in isolated nuclei. We show that while deletions of the H4 and H3 N-termini have similar effects on dam methylase access in the GAL1 coding region, the H4 N-terminal deletion uniquely alters dam access at a region near the TATA element. This change is independent of the transcriptional state of GAL1. In addition, LMPCR analysis of micrococcal nuclease digests of yeast nuclei demonstrate that H4 N-terminal deletion has unique effects on nuclease accessibility in the nucleosomal region upstream of the TATA element. Our results are consistent with the H4 N-terminus mediating activation of GAL1 through its effect on the proximal promoter region near the TATA box. These data also suggest that the H3 N-terminus affects GAL1 hyperactivation through a different promoter element than that affected by H4.
TL;DR: In this paper, the relations between chromatin structure and transcriptional activity of SNR6 genes in vivo were analyzed by micrococcal nuclease digestion and showed a protection of the TATA box, nucle-sensitive sites around the A and B blocks, and arrays of positioned nucleosomes in the flanking regions.
Abstract: Recent work has demonstrated a repressive effect of chromatin on the transcription of the yeast SNR6 gene in vitro. Here, we show the relations between chromatin structure and transcriptional activity of this gene in vivo. Analysis of the SNR6 locus by micrococcal nuclease digestion showed a protection of the TATA box, nuclease-sensitive sites around the A and B blocks, and arrays of positioned nucleosomes in the flanking regions. Analysis of a transcriptionally silent SNR6 mutant containing a 2-bp deletion in the B block showed a loss of TATA-protection and rearrangement or destabilization of nucleosomes in the flanking regions. Hence, SNR6 organizes the chromatin structure in the whole region in a manner dependent on its transcriptional state. Transcriptional analysis was performed by use of maxi-gene SNR6 constructs introduced into histone-mutated strains. Chromatin disruption induced by histone H4 depletion stimulated the transcription of promoter-deficient, but not of wild-type SNR6 genes, revealing a competition between the formation of nucleosomes and the assembly of Pol III transcription complexes that was much in favor of transcription factors. On the other hand, amino-terminal mutations in histone H3 or H4 had no effect (H4) or only a moderate stimulatory effect (H3) on the transcription of promoter-deficient SNR6 genes.
TL;DR: Depletion of maternally-derived histones as the signal for zygotic gene activation is explored and changes in chromatin structure, rather than changes in the activity of the transcriptional apparatus, may underlie the timing and basis forZygosis in the mouse embryo.
TL;DR: The chromatin conformation of somatic and meiotic chromosomes is, at least in part, a function of electrostatic nucleosome interactions that are mediated by transient acetylation of the histone H4 N-terminal domain and phosphorylation of hist one H1.
Abstract: The chromatin conformation of somatic and meiotic chromosomes is, at least in part, a function of electrostatic nucleosome interactions that are mediated by transient acetylation of the histone H4 N-terminal domain and phosphorylation of histone H1. The distribution of those histones in the chromatin of meiotic chromosomes is reported here. Antibodies to testis-specific histone 1, H1t, detect H1t in the chromatin of mouse meiotic prophase chromosomes only after synapsis and synaptonemal complex (SC) assembly is completed and before core separation is initiated. The H1t protein is evenly distributed over euchromatin, heterochromatin and the SC. Antibodies to acetylated lysine residues 5, 12 or 16 of histone H4, indicate that the euchromatin is more acetylated than the centromeric heterochromatin. The pattern is most pronounced for acetylated residue 5 and least for 16. Antibodies to phosphorylated H1 epitopes do not react with chromatin but, instead, recognize the chromosome cores and SCs. Possibly these are not phosphorylated histone H1 epitopes, but SC proteins with similar potentially phosphorylatable sequences such as KTPTK of the synaptic protein Syn1.
TL;DR: It is shown that site I, an element containing both G-rich and ATF-like consensus sequences, confers maximal levels of transcription in proliferating cells and postulate that this site may act to amplify the cell cycle response.
Abstract: The promoter of the cell cycle regulated histone FO108 H4 gene is mediated by two in vivo protein/DNA interaction domains, sites I and II. We have shown previously that site II mediates the cell cycle controlled enhancement of H4 gene transcription at the G1/S phase boundary. Here we show that site I, an element containing both G-rich and ATF-like consensus sequences, confers maximal levels of transcription in proliferating cells. By the combined application of gel shift assays with site-directed mutagenesis, DNase I footprinting, oligonucleotide competition, in vitro expression of recombinant proteins, and specific antibody supershift studies, we demonstrate that the proximal G-rich sequence within site I interacts with the transcription factor Sp1, while the distal portion of site I interacts with members of the ATF family of proteins, including ATF-1. In vitro transcription studies as well as expression assays of transiently and stably transfected genes in HeLa cells reveal that the deletion of site I causes a dramatic decrease in expression. Mutation of the Sp1 element, which abolishes Sp1 binding, results in a 6-10-fold reduction in reporter activity. In addition, overexpression of Sp1 in Sp1-deficient cells results in the dramatic activation of the histone promoter. In contrast, mutation of the asymmetric ATF binding site, located distally within site I, has a more limited effect upon expression. Interestingly, the contribution of the Sp1 site to maximal transcription was cell type dependent. Thus, we demonstrate that the Sp1 binding site of the site I histone H4 promoter in particular is critical for maximal expression in living cells and postulate that this site may act to amplify the cell cycle response.
TL;DR: Intracerebroventricular injections of synthetic histogranin in mice protect them against N-methyl-D-aspartate (NMDA)-induced convulsions without affecting Convulsions induced by (R,S)-alpha-amino-3-hydroxy -5- methyl-4-isoxazole-propionate (AMPA), kainate and bicuculline.
TL;DR: Northern blot analysis of RNA from testicular cells separated by centrifugal elutriation, S1 nuclease mapping, and reverse transcriptase polymerase chain reaction (RT-PCR) amplification show that both the murine and human H4 genes, like the H1t gene, are expressed in testicular Cells, whereas the H4 gene, in contrast to the H2T gene, is expressed in nontesticular human and mouse cell culture cells.
Abstract: Mouse and human H4 genes associated with the testis-specific H1t gene were isolated from genomic libraries and were sequenced. The deduced amino acid sequences are identical to other mouse...
TL;DR: The N-terminal domain of histone H4 has been implicated in various nuclear functions, including gene silencing and activation and replication-linked chromatin assembly as discussed by the authors, and it has been suggested that H4 plays a role in maintaining genome integrity through the cell cycle, possibly by a mechanism involving lysine acetylation.
Abstract: The N-terminal domain of histone H4 has been implicated in various nuclear functions, including gene silencing and activation and replication-linked chromatin assembly. Many of these have been identified by using h4 mutants in the yeast S. cerevisiae. In a recent paper, Megee et al. use this approach to show that mutants in which all four N-terminal H4 lysines are substituted with glutamines accumulate increased levels of DNA damage. A single lysine, but not an arginine, anywhere in the N-terminal domain suppresses this phenotype. It is suggested that histone H4 plays a role in maintaining genome integrity through the cell cycle, possibly by a mechanism involving lysine acetylation.
TL;DR: It is suggested that ionizing radiation does not act as a general protein‐synthesis inhibitor and that the presence of a labile protein is required for the maintenance of specific gene transcription and mRNA accumulation after radiation exposure, especially at high dose‐rates.
Abstract: We performed experiments to determine the effects of ionizing radiation exposure on expression of genes such as beta-actin, c-fos, histone H4, c-myc, c-jun, Rb, and p53 after exposure of Syrian hamster embryo (SHE) cells to the protein synthesis inhibitor cycloheximide. The purpose of these experiments was to determine the role of a labile protein in the radiation-induced response. The results revealed that when ionizing radiation (either fission-spectrum neutrons or gamma rays) was administered 15 min after cycloheximide treatment of SHE cells, the radiation exposure reduced cycloheximide-mediated gene induction of c-fos, histone H4, and c-jun. In addition, dose-rate differences were found when radiation exposure most significantly inhibited the cycloheximide response. Our results suggest that ionizing radiation does not act as a general protein-synthesis inhibitor and that the presence of a labile protein is required for the maintenance of specific gene transcription and mRNA accumulation after radiation exposure, especially at high dose-rates.
TL;DR: It is shown that a generalized decrease and re elevation of the levels of mRNA takes place as part of the apoptotic program, which may be triggered by relaxation of the chromatin caused by alterations in the Chromatin structure of apoptotic cells.
Abstract: The IL-2 dependent murine cytotoxic T cell line CTLL-2 undergoes programmed cell death when deprived of its specific cytokine. We analyzed the expression of cell cycle related genes after IL-2 deprivation. Here we show that a generalized decrease and re elevation of the levels of mRNA takes place as part of the apoptotic program. The levels of several mRNAs encoding cell cycle functions, including cyclin D2, cyclin D3, cyclin B1, c-myc and max all declined at 1.5-3 h following IL-2 deprivation. Notably, the maxmRNA, which was shown to be expressed in proliferating, growth arrested and differentiated cells, is down regulated with the same kinetics as the other mRNAs. Surprisingly, the mRNAs whose levels declined at 1.5-3 h rose again at 10-14 h, a time which closely followed the time of the first detection of apoptotic DNA degradation, at 8 h, but which precedes actual loss of viability, at 14 h, as measured by trypan blue exclusion. Of all analyzed genes only the expression of the S-phase specific histone H4 gene resists the initial decrease and declines gradually over the course of cell death. Measurement of c-Myc protein synthesis at a late stage of the apoptotic program revealed that the accumulated reinduced mRNA is not translated into protein. Because transcriptional regulation has been shown to be dependent on the chromatin structure, the reinduction may be triggered by relaxation of the chromatin caused by alterations in the chromatin structure of apoptotic cells.
TL;DR: In regenerating livers of non-irradiated and irradiated rats, there was a greater rate of acetylation in tetraacetylated subfractions of histone H4 compared with intact livers, and an age-dependent decrease in histone acetyltransferase activity in normal and regenerating rat livers was obvious.
TL;DR: Transcriptional tests indicate that the 0.25 N HCl soluble protein extracts from active chromatin contain activator proteins which are capable of countering the histone suppressors present in the extracts in a DNA base and sequence specific manner.
TL;DR: The results indicate that the H4 cell cycle element (CCE), which mediates S phase‐specific stimulation of H4 gene transcription, is not required for transcriptional regulation during differentiation, and suggests that down‐regulation of histone gene expression during cellular differentiation may be mediated by passive inactivation of the promoter due to loss of positive regulatory factor.
Abstract: We have investigated the promoter element(s) required by the cell cycle regulated FO108 human histone H4 gene for control of gene expression during adipocyte proliferation and differentiation Stable 3T3L1 cell lines were established that express fusion genes in which the histone H4 promoter is joined to chloramphenicol acetyltransferase (cat) as a reporter gene Expression of the H4CAT fusion genes was monitored in proliferating and confluent 3T3L1 preadipocytes and in differentiating 3T3L1 adipocytes The results indicate that the H4 cell cycle element (CCE), which mediates S phase-specific stimulation of H4 gene transcription, is not required for transcriptional regulation during differentiation Instead, a minimal H4 promoter (nucleotides −46 to −11) is sufficient to mediate the complex transcriptional response of H4 gene expression observed during the process of adipocyte differentiation of 3T3L1 cells In addition, the data suggest that down-regulation of histone gene expression during cellular differentiation may be mediated by passive inactivation of the promoter due to loss of positive regulatory factor(s) © 1995 Wiley-Liss, Inc
TL;DR: The effects of gossypol at the genomic level in rat spermatogenic cells is reported to have affected the transcription factors for interaction with site 1 and that no effect was demonstrated in NPE that interacted with site 2.
TL;DR: Gene organization and sequence features indicate that the two Holothuria genes are the equivalents of a known pair of late H2B and H4 genes which have been described in the genome of sea urchins.
Abstract: A genomic library of the sea cucumber Holothuria tubulosa was screened with human and murine histone gene hybridization probes. A recombinant phage carrying an H4 gene was isolated and sequenced. Hybridization analysis of the entire 20 kb phage insert with probes for H1, H2A, H2B and H3 histones was negative except for H2B. This solitary arrangement of the two neighbouring histone H4 and H2B genes is in contrast to the organization of ‘cleavage stage’ histone genes, which are arranged in tandem quintets of genes encoding the 5 histone classes. Gene organization and sequence features indicate that the two Holothuria genes are the equivalents of a known pair of late H2B and H4 genes which have been described in the genome of sea urchins. This result shows that the simultaneous occurrence of tandem repeats of histone gene quintets and smaller groups of structurally distinct histone gene subtypes is not unique for sea urchins, but also applies to other echinodermata, such as the sea cucumber Holothuria tubulosa.
TL;DR: A cDNA encoding a mouse transcription factor IID (TFIID) subunit, containing histone H4 homology, was cloned and sequenced and four putative direct repeats were found in the most highly conserved region in the central part of this protein.
TL;DR: A cDNA encoding a rat transcription factor IID (TFIID) subunit (p80), with histone H4 homology, was isolated and sequenced and predicts a 678-aa protein with 97% identity to the human and 42% to the Drosophila melanogaster (Dm) homologues.
01 Jan 1995
TL;DR: Positioning of nucleosomes adjacent to the α2/MCM1 operator provides a model system for understanding how multiple proteins cooperate in the formation or maintenance of regulatory chromatin structures.
Abstract: Publisher Summary Repression of yeast a cell type specific genes in α cells is tightly linked to the positioning of nucleosomes adjacent to the α2/MCM1 operator. In the presence of α2, nucleosomes are stably and precisely positioned 15 bp from the edge of the operator, incorporating promoter regions of the α cell specific genes. Positioning is propagated downstream for several nucleosomes, reflecting the packaging of these genes into repressive chromatin subdomains. Moreover, mutations in histone H4 that alter nucleosome stability partially derepress a cell specific gene expression, affirming the importance of these nucleosomes to repression. Recent data indicate that several global repressors, including SSN6 and TUP1, are also involved in the organization of chromatin. Positioning of nucleosomes adjacent to the α2/MCM1 operator provides a model system for understanding how multiple proteins cooperate in the formation or maintenance of regulatory chromatin structures. Because packaging of promoter regions into chromatin represses transcription initiation both in vitro and in vivo, much attention has been focused on the interplay between transcriptional activators and chromatin. Indeed, current models of transcriptional activation often invoke nucleosome destabilization via formation of ternary complexes between activator proteins, histone octamers, and DNA.