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 1,081 records · Page 60Linked to original sources
PubMed1983

Binding of benzo(a)pyrene and (+/-)-7 beta,8 alpha-dihydroxy-9 alpha, 10 alpha-epoxy-7,8,9, 10-tetrahydrobenzo(a)pyrene to histones.

AKR-2B mouse embryo cells were incubated for 24 hr with [3H]benzo(a)pyrene, and the histones were isolated and analyzed using one- and two-dimensional gel electrophoresis and autoradiography. The results revealed that (a) histones H1, H2A, and H3 incorporated significant amounts of label whereas little or no label was associated with histones H2B and H4 and (b) electrophoresis of the histones in the Triton:acid:urea gel system caused labeled histones to have a slower migration than did the corresponding unlabeled histones. Additional studies such as incubation of (+/-)-7 beta,8 alpha-[3H]dihydroxy-9 alpha,10 alpha-epoxy-7,8,9,10-tetrahydrobenzo(a)pyrene with nuclei resulted in radioactive labeling of histones H1, H2A, H2B, and H3 and of high-mobility-group proteins HMG1 and HMG2. The low levels of label associated with histone H4 in the whole-cell and nuclear studies were further investigated by incubating isolated histones with (+/-)-7 beta,8 alpha-[3H]dihydroxy-9 alpha,10 alpha-epoxy-7,8,9,10-tetrahydrobenzo(a)pyrene. Under these conditions, negligible amounts of radioactivity were associated with H4, while significant labeling of H1, H2A, H2B, and H3 and other nuclear proteins was observed. The results suggest that factors other than the presence of suitable nucleophilic acceptor sites on the histones may be necessary for carcinogen binding.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗
PubMed1984

Extensive purification and characterization of chromatin-bound histone acetyltransferase from Saccharomyces cerevisiae.

A strong correlation has been established between reversible acetylation of histones and transcriptional activation of chromatin. However, the function of histone acetylation remains unknown. We have approached this question by purifying histone acetyltransferase 15,000-fold from yeast and characterizing it enzymatically. Biochemical properties, including the pH and temperature optima and the Michaelis-Menten constants for both acetyl coenzyme A and histones, are similar to those reported for histone acetyltransferases from higher eukaryotes. Yeast histone acetyltransferase has a native molecular weight of 110,000 as determined by gel filtration and is tightly bound to chromatin. It displays high-substrate specificity for histones. It acetylates all four core histones in the order: H4 greater than H2B greater than H2A. 10-fold higher histone acetyltransferase activity is observed for free histones when compared to yeast polynucleosomes as a substrate.

Acetyltransferases↗
PubMed1980

[Competitive binding of histones to DNA and the problem of chromatin self-assembly].

The competitive binding of histones to DNA in a medium of physiological ionic strength (0.15 M NaCl) and in water was studied by an electrophoretic analysis of histones bound to DNA and retaining their free state in the mixtures of DNA with total histone. In the medium of physiological ionic strength the binding sequences of more and less competitive histone fraction molecules to DNA can be represented as follows: H3+H4, H2a+ +H2b and H3, H4, H2a, H2b and H1, which is indicative of the absence of histone complexes in water and their presence in 0.15 M NaCl, in addition to individual molecules. In water the binding sequences of the histone, molecules to DNA were identical, i. E. H3+H4, H2a, H2b+H1. It was concluded that the non-ionic interaction between the histones bound to DNA determines the discrepancy between the values of histone net charges and their relative affinities for DNA by increasing the correlation between the positively charged amino acid residues of the histones. The relations between the histone competition for DNA and the chromatin self-assembly as well as the reproduction of the specific pattern of gene expression in the cell generation are discussed.

Animals↗
PubMed1980

The identification of distinct populations of acetylated histone.

We have utilized sodium butyrate to inhibit histone deacetylases in order to study the rates of histone acetylation in hepatoma tissue culture cells. In this manner, we have been able to observe two rates of hypermodification of acetylated core histone. By selectively radolabeling acetylated histone fractions based upon differences in their acetate exchange rates, we have identified the rate of histone acetate hydrolysis and the rate of hyperacetylation in 50 mM sodium butyrate for two distinct populations of acetylated histone. One population, comprising no more than 15% of each of the non-H1 histones, is characterized by rapid hyperacetylation (t 1/2 congruent to 7 min for monoacetylated H4) and the rapid (t 1/2 congruent to 3 to 7 min) removal of this modification. A second population is deacetylated with t 1/2 congruent to 30 min and is hypermodified much less vigorously in 50 mM sodium butyrate (t 1/2 congruent 200 to 300 min for monoacetylated H4). Unlike the rapidly metabolized group, the fraction of total histone in this slow population varies between the four core histones. In addition, there appears to be no interconversion of histone between these populations.

Acetates↗
PubMed1979

Histone molar ratios among different electrophoretic forms of mono- and dinucleosomes.

The relative molar ratios of each of the histone classes and protein A24 have been determined in nuclei, chromatin, and different electrophoretic forms of mono- and dinucleosomes of cultured mouse cells. For this purpose, [3H]lysine- and [14C]arginine-labeled cells were used for sample preparations, and stoichiometries were estimated from protein radioactivity profiles and known amino acid compositions following sodium dodecyl sulfate (SDS)-gel electrophoresis. The results demonstrate that upper limits of one and two histone H1 molecules exist per mono- and dinucleosome, respectively. However, isolated nuclei contain less than one copy of histone H1 per nucleosome. In addition, among the chromatin subfractions studied, histones H3, H2B, and H4 are essentially equimolar, while histone H2A is less than equimolar by 19 +/- 9%. This latter finding offers direct support to the proposal of Goldknopf (Goldknopf, I. L., French, M. F., Musso, R., and Busch, H. (1977) Proc. Natl. Acad. Sci. U. S. A. 74, 5492-5495) that protein A24 replaces histone H2A in the octamer protein core of the nucleosome, since about 10% of the total histone H2A of cultured mouse cells is in the form of protein A24 and is present in nucleosomes. From the results of the present study, it is concluded that electrophoretic fractionation of mono- and dinucleosomes is not due to variable molar ratios or amounts of the four smaller histone classes, but depends on part on DNA length, the number of associated histone H1 molecules, and non-histone chromosomal proteins.

Arginine↗
PubMed1993

Presence of histone H2B in Trypanosoma cruzi chromatin.

The organization of chromatin in protists presents some characteristic features. In Trypanosoma cruzi, no condensation of chromatin into chromosomes is observed during cell division. A systematic characterization of histones should provide information on this peculiar behaviour. Histone H2B from this parasite was characterized by selective dissociation from chromatin in 0.8 M NaCl, by its elution pattern in narrow-bore reversed phase high performance liquid chromatography, by polyacrylamide gel electrophoresis and by partial sequencing of its amino terminal domain. This chromosomal protein differs from histone H2B of other species. The first 12 amino acids are missing which explains its lower molecular weight when compared to human histone H2B. Correspondingly, the amino terminal domain of T. cruzi histone H2B is 25-30% shorter than other histones H2B. Moreover, three out of four acetylation sites present in human histone H2B are missing in T. cruzi histone H2B. The differences in size and in acceptor sites for acetylation of T. cruzi histone H2B when compared to human histone H2B may represent a functional feature to consider for the understanding of the chromatin cycle of condensation in this parasite.

Amino Acid Sequence↗
PubMed1994

Enzymatic methylation of recombinant heterogeneous nuclear RNP protein A1. Dual substrate specificity for S-adenosylmethionine:histone-arginine N-methyltransferase.

We have previously reported the existence of two different molecular species of protein methylase I (S-adenosylmethionine:protein-arginine N-methyltransferase, E.C. 2.1.1.23) in calf brain, one specific for myelin basic protein and the other for histone (Ghosh, S. K., Paik, W. K., and Kim, S. (1988) J. Biol. Chem. 263, 19024-19033). In the present study, however, we report that heterogeneous ribonucleoprotein particle protein A1 is most likely an in vivo substrate for the "histone-specific protein methylase I." The unmethylated recombinant protein A1 has been found to be a much superior methyl acceptor for the enzyme than histone with a Km value two orders of magnitude lower (0.19 microM) than that for histone (21 microM). Myelin basic protein, a specific inhibitor for histone protein methylase I, exhibited a lower IC50 for protein A1 methylation (IC50 = 33 microM) compared with histone methylation (IC50 = 220 microM) and competitively inhibited the former with a Ki value of 1.3 x 10(-6) M. The extent of inhibition of protein A1 and histone methylation by the polyclonal antibodies prepared against purified "histone protein methylase I" was identical. Maximally, 1.08-mol methyl groups were incorporated per mol of protein A1, which was 27-fold higher than that of histone (0.04 mol/mol of histone). HPLC analysis of the enzymatically methylated amino acid residues in protein A1 revealed the formation of NG-monomethylarginine and NG,NG-dimethylarginine. The ratio of NG,NG-dimethylarginine/NG-monomethylarginine increased as a function of incubation period; however, NG,N'G-dimethylarginine was not detectable. Proteolytic cleavage of the methyl-3H-labeled recombinant protein A1 by trypsin and Staphylococcus aureus V8 endoprotease indicated that protein A1 possesses multiple sites for methylation, one of which was identified as residue 194 arginine, which coincided with the in vivo methylation site.

Amino Acid Sequence↗
PubMed2001

Induction of histone acetylation in mouse erythroleukemia cells by some organosulfur compounds including allyl isothiocyanate.

In previous studies we observed that some allyl sulfides can cause increased acetylation of histones and differentiation in DS19 mouse erythroleukemia cells. In the present work we observed increased acetylation of histones with allyl isothiocyanate and butanethiol but not with butyl sulfide or butyl disulfide. Increased acetylation of histones was established by change in electrophoretic mobility, incorporation of [3H]acetate or immunoblotting. Histone deacetylase in nuclei of DS19 cells was inhibited 74% by 0.5 mM allyl mercaptan and 43% by 0.5 mM butanethiol but was not significantly affected by 0.5 mM allyl isothiocyanate. There was some degree of reversibility in the effect of allyl isothiocyanate when the cells were incubated for 15 hr in fresh medium. The data suggested that allyl isothiocyanate may stimulate histone acetylation rather than inhibit histone deacetylation. Addition of allyl isothiocyanate, however, had very little or no additional effect on the induction of histone acetylation caused by trichostatin A. Histone acetyltransferase activity determined in cell homogenates was not increased by preincubation of cells with allyl isothiocyanate or inclusion of allyl isothiocyanate in the assay medium. It was concluded that treatment of mouse erythroleukemia cells with allyl isothiocyanate can cause increased acetylation of histones but the mechanism for this effect requires further elucidation.

Acetylation↗
PubMed1997

Nuclear matrix, dynamic histone acetylation and transcriptionally active chromatin.

The nuclear matrix, the RNA-protein skeleton of the nucleus, has a role in the organization and function of nuclear DNA. Nuclear processes associated with the nuclear matrix include transcription, replication and dynamic histone acetylation. Nuclear matrix proteins, which are tissue and cell type specific, are altered with transformation and state of differentiation. Transcription factors are associated with the nuclear matrix, with the spectra of nuclear matrix bound factors being cell type specific. There is compelling evidence that the transcription machinery is anchored to the nuclear matrix, and the chromatin fiber is spooled through this complex. Transcriptionally active chromatin domains are associated with dynamically acetylated histones. The energy exhaustive process of dynamic histone acetylation has several functions. Acetylation of the N-terminal tails of the core histones alters nucleosome and higher order chromatin structure, aiding transcriptional elongation and facilitating the binding of transcription factors to nucleosomes associated with regulatory DNA sequences. Histone acetylation can manipulate the interactions of regulatory proteins that bind to the N-terminal tails of the core histones. Lastly, dynamic acetylation may contribute to the transient attachment of transcriptionally active chromatin to the nuclear matrix. Reversible histone acetylation is catalyzed by histone acetyltransferase and deacetylase, enzymes associated with the nuclear matrix. The recent isolation and characterization of histone acetyltransferase and deacetylase reveals that these enzymes are related to transcriptional regulators, providing us with new insights about how these enzymes are targeted to nuclear matrix sites engaged in transcription.

Acetylation↗
PubMed2004

Histone hypomethylation is an indicator of epigenetic plasticity in quiescent lymphocytes.

Post-translational modifications of histone amino termini are thought to convey epigenetic information that extends the coding potential of DNA. In particular, histone lysine methylation has been implicated in conveying transcriptional memory and maintaining lineage fidelity. Here an analysis of histone lysine methylation in quiescent (G(0)) and cycling lymphocytes showed that methylation of histone H3 at lysines 4 (H3K4), 9 (H3K9), 27 (H3K27) and histone H4 at lysine 20 is markedly reduced in resting B lymphocytes as compared with cycling cells. Quiescent B cells also lacked heterochromatin-associated HP1beta and Ikaros at pericentric chromatin and expressed low levels of Ezh2 and ESET histone methyl transferases (HMTases). Nuclei from resting B or T cells were approximately three times more efficiently reprogrammed in nuclear transfer assays than cells in which HMTase expression, histone methylation and HP1beta binding had been restored following mitotic stimulation. These results showing local and global changes in histone lysine methylation levels in vivo demonstrate that constitutive heterochromatin organization is modified in resting lymphocytes and suggest that histone hypomethylation is a useful indicator of epigenetic plasticity.

Animals↗
PubMed2024

DNA polymerase delta governs parental histone transfer to DNA replication lagging strand.

Chromatin replication is intricately intertwined with the recycling of parental histones to the newly duplicated DNA strands for faithful genetic and epigenetic inheritance. The transfer of parental histones occurs through two distinct pathways: leading strand deposition, mediated by the DNA polymerase ε subunits Dpb3/Dpb4, and lagging strand deposition, facilitated by the MCM helicase subunit Mcm2. However, the mechanism of the facilitation of Mcm2 transferring parental histones to the lagging strand while moving along the leading strand remains unclear. Here, we show that the deletion of Pol32, a nonessential subunit of major lagging-strand DNA polymerase δ, results in a predominant transfer of parental histone H3-H4 to the leading strand during replication. Biochemical analyses further demonstrate that Pol32 can bind histone H3-H4 both in vivo and in vitro. The interaction of Pol32 with parental histone H3-H4 is disrupted through the mutation of the histone H3-H4 binding domain within Mcm2. Our findings identify the DNA polymerase δ subunit Pol32 as a critical histone chaperone downstream of Mcm2, mediating the transfer of parental histones to the lagging strand during DNA replication.

DNA Polymerase III↗
PubMed2002

Disruptor of telomeric silencing-1 is a chromatin-specific histone H3 methyltransferase.

Yeast disruptor of telomeric silencing-1 (DOT1) is involved in gene silencing and in the pachytene checkpoint during meiotic cell cycle. Here we show that the Dot1 protein possesses intrinsic histone methyltransferase (HMT) activity. When compared with Rmt1, another putative yeast HMT, Dot1 shows very distinct substrate specificity. While Rmt1 methylates histone H4, Dot1 targets histone H3. In contrast to Rmt1, which can only modify free histones, Dot1 activity is specific to nucleosomal substrates. This was also confirmed using native chromatin purified from yeast cells. We also demonstrate that, like its mammalian homolog PRMT1, Rmt1 specifically dimethylates an arginine residue at position 3 of histone H4 N-terminal tail. In surprising contrast, methylation by Dot1 occurs in the globular domain of nucleosomal histone H3. Matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) analysis suggests that H3 lysine 79 is trimethylated by Dot1. The intrinsic nucleosomal histone H3 methyltransferase activity of Dot1 is certainly a key aspect of its function in gene silencing at telomeres, most likely by directly modulating chromatin structure and Sir protein localization. In agreement with a role in regulating localization of histone deacetylase complexes like SIR, an increase of bulk histone acetylation is detected in dot1- cells.

Amino Acid Sequence↗
PubMed2005

Thanatos-associated protein 7 associates with template activating factor-Ibeta and inhibits histone acetylation to repress transcription.

The posttranslational modifications of histones on chromatin or a lack thereof is critical in transcriptional regulation. Emerging studies indicate a role for histone-binding proteins in transcriptional activation and repression. We have previously identified template-activating factor-Ibeta (TAF-Ibeta, also called PHAPII, SET, and I(2)(pp2A)) as a component of a cellular complex called inhibitor of acetyltransferases (INHAT) that masks histone acetylation in vitro and blocks histone acetyltransferase (HAT)-dependent transcription in living cells. TAF-Ibeta has also been shown to associate with transcription factors, including nuclear receptors, to regulate their activities. To identify novel interactors of TAF-Ibeta, we employed a yeast two-hybrid screen and identified a previously uncharacterized human protein called thanatos-associated protein-7 (THAP7), a member of a large family of THAP domain-containing putative DNA-binding proteins. In this study we demonstrate that THAP7 associates with TAF-Ibeta in vitro and map their association domains to a C-terminal predicted coiled-coil motif on THAP7 and the central region of TAF-Ibeta. Similarly, stably transfected THAP7 associates with endogenous TAF-Ibeta in intact cells. Like TAF-Ibeta, THAP7 associates with histone H3 and histone H4 and inhibits histone acetylation. The histone-interacting domain of THAP7 is sufficient for this activity in vitro. Promoter-targeted THAP7 can also recruit TAF-Ibeta and silencing mediator of retinoid and thyroid receptors/nuclear hormone receptor corepressor (NCoR) proteins to promoters, and knockdown of TAF-Ibeta by small interfering RNA relieves THAP7-mediated repression, indicating that, like nuclear hormone receptors, THAP7 may represent a novel class of transcription factor that uses TAF-Ibeta as a corepressor to maintain histones in a hypoacetylated, repressed state.

Acetylation↗
PubMed1975

Specific interaction of chromatin non-histone proteins with DNA.

The interaction of different preparations of chromatin non-histone proteins of rat liver and thymus with homologous and heterologous DNA was studied. It is shown by the method of fixation of non-histone proteins-DNA complexes on nitrocellulose filters that: (1) all the non-histone proteins preparations studied form complexes with DNA in 0.02 M Tris--HCl (pH 7.5)--3 mM MgCl2; (2) the main part of non-histone proteins interacting with DNA binds to it non-specifically; (3) a small part of non-histone proteins interacts specifically with the homologous native DNA in 5 M urea; (4) both homologous and heterologous denatured DNA binds non-histone proteins more effectively than the native one; (5) the specific interaction of non-histone proteins with the homologous denatured DNA is observed both without urea and in its presence. The specific interaction of a small part of non-histone proteins with the homologous native and denatured DNA is also shown by the method of non-histone proteins chromatography on polyacrylamide--agarose columns containing DNA. The data obtained are discussed in the light of the possible non-histone proteins role in the specific regulation of the transcription process.

Animals↗
PubMed2004

Histone demethylation mediated by the nuclear amine oxidase homolog LSD1.

Posttranslational modifications of histone N-terminal tails impact chromatin structure and gene transcription. While the extent of histone acetylation is determined by both acetyltransferases and deacetylases, it has been unclear whether histone methylation is also regulated by enzymes with opposing activities. Here, we provide evidence that LSD1 (KIAA0601), a nuclear homolog of amine oxidases, functions as a histone demethylase and transcriptional corepressor. LSD1 specifically demethylates histone H3 lysine 4, which is linked to active transcription. Lysine demethylation occurs via an oxidation reaction that generates formaldehyde. Importantly, RNAi inhibition of LSD1 causes an increase in H3 lysine 4 methylation and concomitant derepression of target genes, suggesting that LSD1 represses transcription via histone demethylation. The results thus identify a histone demethylase conserved from S. pombe to human and reveal dynamic regulation of histone methylation by both histone methylases and demethylases.

Conserved Sequence↗
PubMed2006

New histone incorporation marks sites of UV repair in human cells.

Chromatin organization is compromised during the repair of DNA damage. It remains unknown how and to what extent epigenetic information is preserved in vivo. A central question is whether chromatin reorganization involves recycling of parental histones or new histone incorporation. Here, we devise an approach to follow new histone deposition upon UV irradiation in human cells. We show that new H3.1 histones get incorporated in vivo at repair sites. Remarkably we find that H3.1, which is deposited during S phase, is also incorporated outside of S phase. Histone deposition is dependent on nucleotide excision repair (NER), indicating that it occurs at a postrepair stage. The histone chaperone chromatin assembly factor 1 (CAF-1) is directly involved in the histone deposition process in vivo. We conclude that chromatin restoration after damage cannot rely simply on histone recycling. New histone incorporation at repair sites both challenges epigenetic stability and possibly contributes to damage memory.

Chromatin↗
PubMed2005

Replication-independent histone deposition by the HIR complex and Asf1.

The orderly deposition of histones onto DNA is mediated by conserved assembly complexes, including chromatin assembly factor-1 (CAF-1) and the Hir proteins . CAF-1 and the Hir proteins operate in distinct but functionally overlapping histone deposition pathways in vivo . The Hir proteins and CAF-1 share a common partner, the highly conserved histone H3/H4 binding protein Asf1, which binds the middle subunit of CAF-1 as well as to Hir proteins . Asf1 binds to newly synthesized histones H3/H4 , and this complex stimulates histone deposition by CAF-1 . In yeast, Asf1 is required for the contribution of the Hir proteins to gene silencing . Here, we demonstrate that Hir1, Hir2, Hir3, and Hpc2 comprise the HIR complex, which copurifies with the histone deposition protein Asf1. Together, the HIR complex and Asf1 deposit histones onto DNA in a replication-independent manner. Histone deposition by the HIR complex and Asf1 is impaired by a mutation in Asf1 that inhibits HIR binding. These data indicate that the HIR complex and Asf1 proteins function together as a conserved eukaryotic pathway for histone replacement throughout the cell cycle.

Cell Cycle Proteins↗
PubMed2003

Acetylation of histone H3 at lysine 9 by ethanol in rat hepatocytes.

Histone acetylation plays an important role in transcriptional activation. We have investigated the effect of ethanol on nuclear histone H3 acetylation in rat hepatocytes. Hepatocytes were incubated with ethanol (5-200 mM) for 24h and then acetylation states of nuclear histone H3 at specific lysine residues (Lys(9) and Lys(14)) were measured by immunoblot analysis using site-specific antibodies. Ethanol increased acetylation of histone H3 at Lys(9) in a dose-dependent manner; 3-fold at 5mM and maximum of 8-fold at 100mM. Sensitivity to low dose of ethanol was remarkable. This ethanol-induced acetylation was also time-dependent, showing a maximal response at 24h. Ethanol did not alter the level of histone H3 expression. Trichostatin A, a histone deacetylase inhibitor, was used as a positive control and it also increased acetylation. However, acetylation at Lys(14) was not affected by ethanol. Treatment of cells with ethanol metabolizing enzyme inhibitors (4-methylpyrazole and cyanamide) decreased ethanol-induced histone H3 acetylation at Lys(9). This is the first report of ethanol-induced selective, post-translational acetylation of histone H3 at Lys(9). This is not due to increased histone expression or a direct physical effect of ethanol but is dependent on ethanol metabolism.

Animals↗