Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “HISTONES”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,009 records · Page 56Linked to original sources
PubMed1978

Sea urchin nuclei use RNA polymerase II to transcribe discrete histone RNAs larger than messengers.

RNA transcribed in isolated sea urchin nuclei and assayed by hybridization to histone genes cloned in E. coli contains sequences homologous to each of the five histone genes. Histone RNA is synthesized exclusively from the same DNA strand which is the template in vivo. Synthesis of the histone gene transcripts is sensitive to alpha-amanitin concentrations which inhibit RNA polymerase II activity. The fraction of histone RNA synthesized in vitro is comparable at two developmental stages to the fraction synthesized in vivo. The nuclear histone transcripts contain sequences homologous to spacer DNA regions present between the coding regions of the 6500 base pair (bp) histone gene repeat unit. The transcription of spacer sequences was demonstrated by hybridization of the nuclear transcripts to subcloned spacer DNA. Although the bulk of the RNA transcripts are greater than 2000 bases long, the histone-specific transcripts are of discrete sizes ranging from 100 bases to about 1100 bases long. Each histone gene hybridizes with at least one of the larger transcripts and with a different subset of smaller RNAs. We do not detect any giant polycistronic transcript spanning the entire histone repeat unit.

Amanitins↗
PubMed1979

Evidence for the formation of nucleosome-like histone complexes on single-stranded DNA.

Using histones reconstituted with RNA and DNA celluloses, we have shown elsewhere that histones elute identically with salt from single- and double-stranded DNA, but differently from RNA (Palter and Alberts, 1979). In this paper we characterize further the suspected specific binding interactions between histones and single-stranded DNA. Nuclease digestion of complexes of histone reconstituted with single-stranded DNA generates only a small yield of discrete (approximately 9S) particles. We can, however, efficiently obtain such 9S "nucleosome-like" complexes when nuclease treatment is avoided and histones are reconstituted directly with short single-stranded DNA pieces. Strikingly, these 9S subunits contain an equimolar composition of the four nucleosomal histones. When these subunits are visualized in the electron microscope, they appear as globular particles which are morphologically indistinguishable from normal mononucleosomes. Based on their sedimentation properties, histone-to-DNA ratio, histone composition and particle diameter, we conclude that they represent an octamer of the four histones (containing two molecules of each histone) associated with single-stranded DNA. These data, viewed in the context of other information concerning chromatin, suggest that nucleosome cores may become transiently bound to single strands of DNA as DNA and RNA polymerases pass.

Binding Sites↗
PubMed1982

Molar proportions and relative rates of synthesis of histones in rat testis.

The molar proportions and relative rates of synthesis of histones in normal and hypophysectomized rat testis seminiferous epithelial cells were determined. After hypophysectomy the molar proportions of histones H1, H2B and (H2A + protein A24) in seminiferous epithelial cells of rat testis increased while their corresponding variants TH1-x, TH2B-x and X2 decreased, but the molar proportions of major-class histones (i.e., sum of subfractions) remained relatively constant and similar to the proportions in somatic cells. The apparent molar proportions of the labeled histones, determined immediately after 2-h periods of [3H]leucine incorporation, were much higher relative to H4 than the proportions of total histones determined by dye binding. The values, however, approached the molar proportions of total histones when rats were killed 11 days after the [3H]leucine injection. Two-dimensional gel electrophoresis confirmed that the high initial molar proportions relative to H4 by [3H]leucine incorporation were not due to the possible contamination by highly-labeled non-histone proteins. The specific activity of histone H4 relative to the specific activity of DNA, determined immediately after 3-h periods of [3H]leucine and [14C]thymidine incorporations was similar to the value when rats were killed 13 days after the injections. It is proposed that histones of seminiferous epithelial cells are synthesized disproportionally relative to H4 and in excess of the quantities required for polynucleosome assembly. The excess histones are subsequently displaced or degraded slowly.

Animals↗
PubMed1984

Organization of Xenopus histone gene variants within clusters and their transcriptional expression.

Using previously cloned Xenopus nucleosomal core histone genes as hybridization probes, a genomic DNA library of Xenopus laevis was screened for histone gene clusters. From over 200 histone-gene containing clones identified, 36 were selected as possibly containing H1 histone genes by hybridization to a probe derived from a sea urchin H1 histone gene. These 36 clones were further analyzed by hybrid-selected translation for the definitive presence of H1 histone genes. The genes for three different H1 histone variants were found: H1A , H1B and H1C . Mapping of the histone genes within each clone showed that at least three different gene arrangements can occur within a cluster and that the type of H1 histone variant present in a cluster may be related to the cluster type. S1-mapping experiments indicated that histone genes found in different cluster-types can be expressed in oocytes. Also, the H1 gene found in one cluster-type was expressed in at least three different cell-types: oocytes, gastrula-stage embryos, and erythroblasts.

Animals↗
PubMed1990

Dynamic histone acetylation in alfalfa cells. Butyrate interference with acetate labeling.

Dynamic histone acetylation of alfalfa (Medicago sativa) was studied in suspension cultures by short-term labeling with radioactive acetate. The relative labeling rates for the acetylated histones were in order of decreasing incorporation; H3.2 greater than H3.1 greater than H4 greater than H2B.1 greater than H2A.3. Histone H3 showed at least seven sites of acetylation, histone H2B.1 had six sites and histone H4 had five sites. Low numbers of acetylation sites were observed for histone H2B.2 and all histone H2A variants. The mass ratio, steady state acetylation and dynamic acetylation between major variant H3.1 and minor variant H3.2 were approx. 2:1, 1:2 and 2:5, respectively. Treatment of alfalfa cells with 50 mM n-butyrate did not lead to histone hyperacetylation, but instead interfered with histone acetylation labeling by acetate. The extent of apparent inhibition increased with time and concentration of butyrate. It is likely that the conversion of butyrate to acetylCoA results in dilution of the specific radioactivity of [3H]acetate in the acetylCoA pool thereby inhibiting the labeling reaction. This interpretation is supported by 14C-labeling of alfalfa acetylated histones by [1-14C]butyrate.

Acetates↗
PubMed2005

Oxidative stress is involved in inhibition of copper on histone acetylation in cells.

Our previous study demonstrates that copper induces histone hypoacetylation by inhibiting histone acetyltransferase (HAT) activity. However, it lacks direct evidences whether copper-inhibited histone acetylation right contributes to the toxicity of copper. Exposure of human leukemia cells (HL-60) to Cu2+ resulted in cell proliferation arrest and a concentration- and time-dependent decrease of histone acetylation. At the same time, Cu2+-induced significant increase of H2O2 and O2.- generation via a concentration- and time-dependent manner too. The histone acetylation was efficiently suppressed by exogenous H2O2, and enhanced by superoxide dismutase (the scavenger of O2.-), catalase (the scavenger of H2O2) or the combination of both, indicating that Cu2+ at least partially inhibited histone acetylation through triggering oxidative stress. Further studies found that sodium butyrate, the inhibitor of histone deacetylase (HDAC), which had no obvious effect on oxidative stress but increased histone acetylation at the concentration of 50 microM, attenuated Cu2+-inhibited cell proliferation, indicating that histone acetylation inhibition is simultaneously involved in the cytotoxicity of Cu2+. Considering the important role of histone acetylation in gene transcription and regulation of cell fate, the present study may open a new door to further understand the mechanism of Cu2+-induced toxicity.

Acetylation↗
PubMed2006

The malaria parasite Plasmodium falciparum histones: organization, expression, and acetylation.

Histones are the building units of nucleosomes and play essential roles in DNA replication, repair and transcription. A comprehensive analysis of histone genes revealed that the Plasmodium falciparum genome encodes a canonical form of each core histone and four histone variants H2A.Z, H3.3, centromere-specific H3 (CenH3), and H2Bv. Mass spectrometry confirmed the synthesis of all histones except CenH3. Real-time reverse transcriptase-polymerase chain reaction and immunoblotting detected a dramatic increase in core histone gene expression during the late trophozoite stages, consistent with their role in replication-related nucleosome assembly. In contrast, the expression of variant histones decreased in mid- or late trophozoite stages. The N-terminal tails of histones participate in transcription regulation through covalent modifications, especially at the lysine residues. In accordance, mass spectrometry analysis revealed acetylation of lysines and methylation of lysines and arginines in the N-termini of H3, H3.3, and H4. Moreover, we identified a new pattern of lysine modifications of the H2A.Z variant. Using a panel of acetylation-specific antibodies, we found that K5, K8, and K12 of H4 were abundantly acetylated at a relatively steady level throughout the erythrocytic cycle. In comparison, the H3-K9 acetylation increased in late trophozoite and schizont stages, while H4-K16 acetylation peaked in mid-trophozoite stage. We have also shown that despite the sequence divergence in the PfH3 N-terminus from their mammalian homologues, the recombinant PfH3 was still efficiently acetylated by both recombinant and native PfGCN5 at K9 and K14. This study suggests that histone replacement and the dynamic histone modifications play important roles in regulating gene expression during erythrocytic development of the malaria parasite.

Acetylation↗
PubMed2006

A novel mechanism for drug-induced liver failure: inhibition of histone acetylation by hydralazine derivatives.

BACKGROUND/AIMS: The aim of this study was to investigate the precise mechanism of liver failure by hydralazine derivatives, with special reference to liver regeneration failure. METHODS: Histone acetylation and proliferation of hepatocytes were evaluated by immunohistochemistry with anti-acetylated histone H4 and proliferating cell nuclear antigen (PCNA). Inhibition of histone acetylation by drugs was determined by in vitro histone acetylation assay. Mice livers fed with todralazine for 1 or 4 months were subjected to immunohistochemistry and Western blotting. Todralazine-fed mice were challenged with anti-Fas to check liver regeneration failure. RESULTS: On immunohistochemistry, histone acetylation in the hepatocytes was significantly impaired in patients with hydralazine derivatives. In an in vitro acetyl transferase assay, histone acetylation was inhibited by hydralazine derivatives in a dose-dependent manner. Mice fed with todralazine (3mg/day) for 4 months showed impairment of histone acetylation in hepatocytes whereas no inhibition was observed in mice fed with todralazine for 1 month. Anti-Fas challenge to todralazine-fed mice resulted in impairment of liver regeneration in respect of liver weight loss with impairment of histone acetylation in hepatocytes. CONCLUSIONS: Todralazine could inhibit catalysis of histone acetyltransferase and long-term administration of todralazine may impair histone acetylation of the hepatocytes, resulting in liver regeneration failure.

Acetylation↗
PubMed2005

Trypanosoma cruzi histone H1 is phosphorylated in a typical cyclin dependent kinase site accordingly to the cell cycle.

Histone H1 of most eukaryotes is phosphorylated during the cell cycle progression and seems to play a role in the regulation of chromatin structure, affecting replication and chromosome condensation. In trypanosomatids, histone H1 lacks the globular domain and is shorter when compared with the histone of other eukaryotes. We have previously shown that in Trypanosoma cruzi, the agent of Chagas' disease, histone H1 is phosphorylated and this increases its dissociation from chromatin. Here, we demonstrate using mass spectrometry analysis that T. cruzi histone H1 is only phosphorylated at the serine 12 in the sequence SPKK, a typical cyclin-dependent kinase site. We also found a correlation between the phosphorylation state of histone H1 and the cell cycle. Hydroxyurea and lactacystin, which, respectively, arrest parasites at the G1/S and G2/M stages of the cell cycle, increased the level of histone H1 phosphorylation. Cyclin-dependent kinase-related enzymes TzCRK3, and less intensely the TzCRK1 were able to phosphorylate histone H1 in vitro. Histone H1 dephosphorylation was prevented by treating the parasites with okadaic acid but not with calyculin A. These findings suggest that T. cruzi histone H1 phosphorylation is promoted by cyclin dependent kinases, present during S through G2 phase of the cell cycle, and its dephosphorylation is promoted by specific phosphatases.

Amino Acid Sequence↗
PubMed2006

Post-translational modifications of Trypanosoma cruzi histone H4.

Histone tails provide sites for a variety of post-translational modifications implicated in the control of gene expression and chromatin assembly. As both histones and control of gene expression in trypanosomes are highly divergent compared to most eukaryotes, post-translational modifications of Trypanosoma cruzi histones were investigated. After in vivo incubation of live parasites with radiolabeled precursors, histone H4 mainly incorporates [(3)H]-acetyl, and to a lesser extent [(3)H]-methyl residues. In contrast, histone H3 preferentially incorporates [(3)H]-methyl residues. The modifications of histone H4 were further characterized by mass spectrometry. MALDI-TOF-TOF-MS analysis revealed that peptides from histone H4 amino-terminus, obtained by either endoproteinase Glu-C or endoproteinase Arg-C digestion, contain isoforms with 14 and 42Da additions, suggesting the presence of simultaneous acetylations and/or methylations. Tandem mass spectrometry analysis demonstrated that the N-terminal alanine is methylated, and lysine residues at positions 4, 10, 14 and 57 are acetylated; lysine at position 18 is mono-methylated, while arginine at position 53 is dimethylated. Immunoblotting analyses using specific antibodies raised against synthetic and acetylated peptides of T. cruzi histone H4 indicate that lysine 4 is acetylated in the majority of histone H4, while other acetylations at the N-terminus portion of histone H4 are less abundant.

Acetylation↗
PubMed2005

The effects of anti-histone H1 antibody on immune cells responsible for rejection reaction.

We previously demonstrated the immunosuppressive activity of anti-histone H1 autoreactive antibodies (Ab) transiently induced in serum of a rat tolerogenic orthotopic liver transplantation (OLT) model. In the present study, we investigated the effects of anti-histone H1 Ab on dendritic cells (DCs), T-cells, lymphokine-activated killer (LAK) cells, and human natural killer (NK) cells. The effects of anti-histone H1 Ab on Concanavalin A (ConA) blast, on rat DC cytokine profiles and phenotypes, and on T-cells, LAK cells, and human NK cells were examined by flow cytometry and RT-PCR. The cytotoxicity of LAK and NK cells pretreated with anti-histone H1 Ab was assayed. The addition of anti-histone H1 Ab to ConA blast inhibited the proliferation of 5-(6)-carboxy-fluorescein succinimidyl ester (CFSE)-labeled lymphocytes without toxicity but increased the population of CD4+CD25+ T-cells. DCs treated with anti-histone H1 Ab expressed lower levels of CD80/CD86, IL-1beta, and IL-6. The addition of anti-histone H1 Ab to LAK culture decreased the percentages of NKR-P1 populations and down-regulated levels of inducible nitric oxide synthase (iNOS), IL-2, and INF-gamma in RT-PCR. The cytotoxicity of LAK and NK cells was lower when pretreated with anti-histone H1 Ab than when pretreated with control IgG. We found that the blockade of histone H1 modulated DCs toward tolerogenic status, decreased the cytotoxicity of LAK and NK cells, and induced CD4+CD25+ T-cells. These results suggest that the use of anti-histone H1 Abs might be a useful strategy for the development of a form of immunosuppression.

Animals↗
PubMed2004

4-Hydroxynonenal oxidatively modifies histones: implications for Alzheimer's disease.

There is increasing evidence of DNA oxidation and altered DNA repair mechanisms in Alzheimer's disease (AD) brain. Histones, which interact with DNA, conceivably could provide a protective shield for DNA against oxidative stress. However, because of their abundant lysine residues, histones may be a target for 4-hydroxynonenal (HNE) modification. In this study, we have shown that HNE binds to histones and that this binding affects the conformation of the histone, measured by electron paramagnetic resonance in conjunction with a protein-specific spin label. The covalent modification to the histone by HNE affects the ability of the histone to bind DNA. Interestingly, acetylated histones appear to be more susceptible to HNE modifications than control histones. Conceivably, altered DNA-histone interactions, subsequent to oxidative modification of histones by the lipid peroxidation product HNE, may contribute to the vulnerability of DNA to oxidation in AD brain.

Acetylation↗
PubMed2000

Studies on the prolactin-releasing mechanism of histones H2A and H2B.

In previous studies we demonstrated that histone preparations possess multiple effects in vivo on pituitary hormone secretion. We have now studied the specificity and signal transduction pathways involved in the prolactin (PRL)-releasing activity of histones H2A and H2B on perifused and incubated rat pituitary cells. In the perifusion experiments, freshly dispersed pituitary cells were packed into short columns and were continuously perifused with serum-free medium. The substances to be tested (stimuli) were pumped through the perifusion circuit, at the end of which perifusate fractions were collected and PRL measured by specific RIA. In the incubation studies, freshly dispersed pituitary cells were incubated in a metabolic incubator with different stimuli at different doses and for varying times. Perifusion of cells with median eminence extract (1/30), histone H2A (30 microM) or histone H2B (30 microM), generated clear PRL release responses. Cells incubated with histone H2A and H2B showed a dose- and time-dependent stimulatory effect on PRL release which, for H2A, was blocked by peptide MB-35, an 86-120 amino acid synthetic fragment of histone H2A. The polycation, poly-lys was unable to mimic the action of histones. To detect the possible signal transduction pathways involved in the response of lactotrophs to histones, cells were incubated with the calcium ionophore A23187, the calcium chelator EGTA, the intracellular phosphoinositide enhancer LiCl, the intracellular cAMP enhancers caffeine, NaF and forskolin, and the protein kinase C inhibitor, trifluoperazine (TFP). Both EGTA (or EGTA plus A23187 ionophore) and TFP were able to reduce significantly the response of lactotrophs to histones. Our results confirm previous evidence that histones may act as hypophysotropic signals. The data also suggest that calcium- and diacylglycerol-associated pathways participate in these effects.

Animals↗
PubMed2001

Developmentally-regulated interaction of a transcription factor complex containing CDP/cut with the early histone H3 gene promoter of the sea urchin Tetrapygus niger is associated with changes in chromatin structure and gene expression.

During sea urchin embryogenesis the early histone genes are temporally expressed to accommodate the high demand for histone proteins during DNA replication at early cleavage stages of development. The early histone genes are transcriptionally active from the 16-cell stage, reaching a peak in expression at the 128-cell stage that gradually decreases until expression is completely inhibited at the late blastula stage. We are studying the gene regulatory mechanisms that control early histone gene expression in sea urchins to understand the interrelationships between chromatin remodeling and transcriptional activation during development. Here, we have investigated chromatin organization and transcription factor interactions by analyzing nuclease hypersensitivity and protein binding in the promoter region of the early histone H3 gene from the sea urchin Tetrapygus niger. We have found a DNase I hypersensitive domain centered at -90 in the early histone H3 gene promoter which is only detected in embryos at the 128-cell stage expressing high levels of early histone H3 mRNA. This hypersensitive site (-110 to -70) encompasses two regulatory elements (TnH3NFH3.1 and TnH3CCAAT). The -94 to -77 region of the histone H3 promoter is recognized by a transcription factor complex in nuclear extracts from 128-cell embryos. Methylation interference analysis and competition studies demonstrated a specific interaction at the CCAAT sequence. Using specific antibodies we find that the homeodomain transcription factor CDP/cut is the DNA-binding component of the complex interacting with the early histone H3 gene promoter in T. niger. Our results provide further evidence for the functional role of CDP/cut in developmental regulation of histone gene expression in phylogenetically diverse eukaryotic species.

Animals↗
PubMed1997

Histone-like transcription factors in eukaryotes.

Histone proteins have long been recognized as important regulators of eukaryotic gene expression. Condensation of DNA into chromatin by the core (H2A, H2B, H3, H4) and linker (H1, H5) histones effectively represses transcription initiation from the promoters of genes that have been packaged. Recently, eukaryotic transcriptional activators and coactivators (both positive and negative) resembling core and linker histone proteins have been discovered. Substantial progress has been made on structural and mechanistic studies of histones and histone-like transcription factors. Three-dimensional structures solved include the core histone octamer, an archael histone homodimer, two core histone-like subunits of transcription factor IID, a linker histone, and a linker histone-like transcriptional activator.

Amino Acid Sequence↗
PubMed2003

Transcriptional activation of the enterocyte differentiation marker intestinal alkaline phosphatase is associated with changes in the acetylation state of histone H3 at a specific site within its promoter region in vitro.

Enterocyte differentiation is thought to occur through the transcriptional regulation of a small subset of specific genes. A recent growing body of evidence indicates that post-translational modifications of chromatin proteins (histones) play an important role in the control of gene transcription. Previous work has demonstrated that one such modification, histone acetylation, occurs in an in vitro model of enterocyte differentiation, butyrate-treated HT-29 cells. In the present work, we sought to determine if the epigenetic signal of histone acetylation occurs in an identifiable pattern in association with the transcriptional activation of the enterocyte differentiation marker gene intestinal alkaline phosphatase (IAP). HT-29 cells were maintained under standard culture conditions and differentiated with sodium butyrate. The chromatin immunoprecipitation (ChIP) assay was used to compare the acetylation state of histones associated with specific regions of the IAP promoter in the two cell populations (undifferentiated vs. differentiated). Chromatin was extracted from cells and cleaved by sonication or enzymatic digestion to obtain fragments of approximately 200 to 600 base-pairs, as confirmed by polymerase chain reaction using primers designed to amplify the IAP segments of interest. The ChIP assay selects DNA sequences that are associated with acetylated histones by immunoprecipitation. Unbound segments represent DNA sequences whose histones are not acetylated. After immunoprecipitation, sequences were detected by radiolabeled polymerase chain reaction, and the relative intensity of the bands was quantified by densitometry. The relative acetylation state of histones at specific sites was determined by comparing the ratios of bound/unbound segments. We determined that in a segment of the IAP promoter between -378 and -303 base-pairs upstream from the transcriptional start site, the acetylation state of histone H3 increased twofold in the differentiated, IAP expressing cells, whereas that of histone H4 remained essentially constant. Additionally, at a distant site, between -1378 and -1303 base-pairs, the acetylation state of H3 and H4 did not change appreciably between the undifferentiated and differentiated cells. We conclude that butyrate-induced differentiation is associated with specific and localized changes in the histone acetylation state within the IAP promoter. These changes within the endogenous IAP gene may underlie its transcriptional activation in the context of the enterocyte differentiation program.

Alkaline Phosphatase↗
PubMed2001

Variability of sperm specific histones in sea urchins.

The variability of sperm histones was compared in two species of sea urchin. Whole sperm specific histones (SpH), were isolated from Tetrapygus niger (Arbacoida) and Parechinus angulosus (Echinoida). Individual histones were purified by chromatography on BioGel P-60 followed by reverse high pressure liquid chromatography (HPLC). The heterogeneity of each major histone type from T. niger was established from their HPLC elution patterns and further confirmed by electrophoresis in polyacrylamide gels containing 6 mM Triton X-100 combined with a transverse urea gradient (0--8 M). In T. niger, as well as in P. angulosus, a single form of SpH1 and SpH2A were found. In contrast, SpH2B was found to be heterogeneous, but represented by one major form in both species. The relatedness between both sets of histones was determined by establishing their immunological cross-reactivity. In this context, polyclonal antibodies elicited against T. niger sperm histones were assayed against individual histones from P. angulosus. From the results obtained, it emerged that histone SpH2A was the more closely related protein between these two species, followed by histone SpH1. In contrast, histone SpH2B was found to be only moderately related. These results confirm that SpH2A did not co-evolve with SpH2B, as was predicted for most species.

Animals↗
PubMed1982

Ultraviolet light induced preferential cross-linking of histone H3 to deoxyribonucleic acid in chromatin and nuclei of chicken erythrocytes.

Histones have been cross-linked to DNA in chicken erythrocyte nuclei and chromatin by using ultraviolet light irradiation at 254 nm. Following irradiation, cross-linked histone-DNA adducts were isolated and purified by hydroxylapatite chromatography, and the DNA component was subjected to acid hydrolysis. Of several hydrolysis techniques investigated, trichloroacetic hydrolysis of the DNA component of the adducts was found to be most effective. Histones isolated from hydrolyzed histone-DNA adducts were characterized by gel electrophoresis and fingerprint analysis. No histone-histone protein adducts were observed. All histone fractions have been shown to cross-link DNA in nuclei or chromatin by utilizing the technique employed, but with different propensities. The order of observed cross-linking, deduced from kinetic experiments, is H1 + H5, H3 greater than H4 greater than H2A much greater than H2B. The preferential binding of the core histone H3, as compared to the other core histones, is discussed in light of recent data concerning histone-DNA interactions and nucleosome structure. The use of the ultraviolet light technique as a conformational probe to study chromatin is also discussed.

Animals↗