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PubMed1985

Effect of inhibition of DNA synthesis on histone synthesis, turnover, and deposition in the rat testis.

In testicular seminiferous epithelial cells (SEC) of normal and hypophysectomized rats, 1-beta-D-arabinofuranosylcytosine and hydroxyurea (at concentrations which inhibited DNA synthesis nearly completely) inhibited histone synthesis only partially, and to a different extent for each histone fraction. In the presence of the inhibitors, the extent of synthesis relative to the corresponding control was TH1-x greater than H1 greater than TH2B-x = X2 = H2A greater than H2B = H3 greater than H4, in which synthesis of the H4 fraction was about 50% of control and that of TH1-x was 90-95% of control. The extent of inhibition of synthesis of each histone fraction was similar after hypophysectomy and, therefore, the changing of the relative populations of heterogeneous cells in the SEC did not influence the relative effects of the inhibitors of DNA synthesis on the synthesis of the various histone fractions. After [3H]leucine injection, the molar proportions of labeled histones relative to H4 decreased markedly between 1.5 h and 6-15 days; this finding indicated that there was rapid removal of histones compared to the H4 fraction during this period. When [14C]thymidine was injected 24 h prior to hydroxyurea treatment and [3H]leucine injection, the ratios of specific activities of histone H4 to DNA did not change significantly over an 11-day period. It appears that newly synthesized histone H4 and other somatic histones are associated with existing DNA in the presence of DNA inhibitors.

Animals↗
PubMed1975

Comparison between histones FV and F2a2 of chicken erythrocyte. II. Interaction with homologous DNA.

The conformation and stability of artificial complexes between chicken erythrocyte DNA and homologous histones FV and F2a2 was studied by circular dichroism (CD) and thermal denaturation followed by both absorbance and CD measurements. The complexes are made after a stepwise potassium fluoride gradient dialysis without urea and studied at low ionic strength (10-minus 3 M). 1) No structural changes of the DNA can be detected up to r equals 0.2 with FV and r equals 0.6 for F2a2. With FV at higher values of r the CD spectrum is altered, indicating the organization of DNA and histones in some kind of aggregate. 2) The conformation of histone molecules inside the complexes is not related to the ionic strength of the medium but to an effective ionic environment close to 0.1 M. This ionic strength would also correspond to the melting temperature of histone-covered DNA. 3) From the analysis of the absorbance melting profile the length of DNA covered with an histone molecule can be estimated. A good agreement is found between the negative charge of this piece of DNA and the net positive charge of the histone. 4) Since the CD transition at 227 nm occurs before the second absorbance transition at 280 nm, the DNA is stabilized no longer by native histone but partially or fully denatured histones. The helical regions of the histone molecule are not involved in the binding process, which appears to be almost purely coulombian and most likely related to some structural fit between the pattern of negative charges in the DNA helix and that of positive charges along the peptide chain.

Animals↗
PubMed1976

Effects of estrogen on gene expression in the chick oviduct. Isolation and fractionation of chromatin non-histone proteins.

Non-histones isolated from hen oviduct chromatin have been fractionated by a variety of methods. Chromatin was dissociated in 2 M NaC1, 5 M Urea, 0.1% beta-mercaptoethanol and 0.01 M Tris - HC1, pH 8.3, and the DNA removed by ultracentrifugation. After desalting by gel filtration the chromatin proteins were separated into three distinct fractions by stepwise elution with 0.10 M NaC1, 0.25 M Na C1 and 15% guanidine - HC1 from Bio-Rex 70 columns. Fractions I and II contain only non-histones and Fraction III contains histones plus a small amount of non-histones. Further fractionation of the non-histones was achieved by ammonium sulfate precipitation and DEAE-cellulose chromatography for Fraction I and phosphocellulose chromatography and gel filtration on Bio-Gel A-15 m for Fraction II. The histone and non-histones present in Fraction III were separated by gel filtration on Bio-Gel A-0.5 m. All fractionation methods have been used preparatively with reasonable recoveries of protein (greater than or equal to 60%). The fractions have been characterized by acrylamide gel electrophoresis. The integrity of the histones was maintained during the fractionation procedure indicating that proteolytic degradation was unlikely to have occurred. There was no selective loss of chromatin proteins during the ultracentrifugation and desalting steps and the non-histones were separated into distinct fractions with enrichment of some species not apparent prior to fractionation of the chromatin proteins.

Animals↗
PubMed1981

Subcellular localisation and properties of histone phosphate phosphatase in human polymorphonuclear leukocytes: alterations in pregnancy and chronic granulocytic leukaemia and relationship to alkaline phosphatase.

Using [32P]histone as substrate, an assay for histone phosphate phosphatase was optimised for human polymorphonuclear leukocytes. Kinetic studies showed that the activity was optimal at pH 6.8, was stimulated by Mn2+ and Co2+, and inhibited by sodium sulphite and zinc chloride. The apparent Km of the enzyme for histone phosphate was 0.89 mumol/l. Neutrophils were homogenized in isotonic sucrose and, after low speed centrifugation, the supernatant was subjected to analytical subcellular fractionation. Gradient fractions were assayed for principal marker enzymes and for histone phosphate phosphatase. Histone phosphate phosphatase activity was shown to be solely located to the cytosol. No activity was detected in the alkaline phosphatase-containing granules. Neutrophils were isolated from the blood of control subjects, patients with chronic granulocytic leukaemia and women in the third trimester of pregnancy. The specific activity (milliunits/mg protein) of histone phosphate phosphatase was significantly reduced in patients with chronic granulocytic leukaemia compared to control values but this decrease was considerably less than that found for alkaline phosphatase. The possible implication of the reduced histone phosphatase activity in leukaemia neutrophils is discussed. There was no significant change in histone phosphate phosphatase in leucocytes from pregnant women. These results, together with the subcellular fractionation experiments and inhibitor studies, strongly indicate that histone phosphate phosphatase is not attributable to neutrophil alkaline phosphatase.

Alkaline Phosphatase↗
PubMed1984

Histone rearrangements accompany nuclear differentiation and dedifferentiation in Tetrahymena.

Histone synthesis and deposition into specific classes of nuclei has been investigated in starved and conjugating Tetrahymena. During starvation and early stages of conjugation (between 0 and 5 hr after opposite mating types are mixed), micronuclei selectively lose preexisting micronuclear-specific histones alpha, beta, gamma, and H3F. Of these histones, only alpha appears to accumulate in micronuclear chromatin through active synthesis and deposition during the mating process. Curiously, alpha is not observed (by stain or label) in young macronuclear anlagen (4C, 10 hr of conjugation). Thus, young macronuclear anlagen are missing all of the histones which are known to be specific to micronuclei of vegetative cells. By 14-16 hr of conjugation, we observe active synthesis and deposition of macronuclear-specific histones, hv1, hv2, and H1, into new macronuclear anlagen (8C). Thus macronuclear differentiation seems well underway by this time of conjugation. It is also in this time period (14-16 hr) that we first detect significant amounts of micronuclear-specific H1-like polypeptides beta and gamma in micronuclear extracts. These polypeptides do not seem to be synthesized during this period, which suggests that beta and gamma are derived from a precursor molecule(s). Since these micronuclear-specific histones do not appear in micronuclear chromatin until after other micronuclei have been selected to differentiate as macronuclei, we suspect that micronuclear differentiation is also an important process which occurs in 10-16 hr mating cells. Our results also suggest that proteolytic processing of micronuclear H3S into H3F (which occurs in a cell cycle dependent fashion during vegetative growth) is not operative during most if not all of conjugation. Thus micronuclei of mating cells contain only H3S which also seems consistent with the fact that some micronuclei differentiate into new macronuclei (micronuclear H3S is indistinguishable from macronuclear H3). Interestingly, the only H3 synthesized and deposited into the former macronucleus of mating cells is the relatively minor macronuclear-specific H3-like variant, hv2. These results demonstrate that significant histone rearrangements occur during conjugation in Tetrahymena in a manner consistent with the fact that during conjugation some micronuclei eventually differentiate into new macronuclei. Our results suggest that selective synthesis and deposition of specific histones (and histone variants) plays an important role in the nuclear differentiation process in Tetrahymena.

Animals↗
PubMed1987

Histone modifications accompanying the onset of developmental commitment.

In the sea urchin, Strongylocentrotus purpuratus, three cell types comprise the 16-cell stage embryo: micromeres, macromeres, and mesomeres. We have analyzed these three cell types for nuclear proteins that were synthesized during the earliest stages of embryonic development. The most striking differences in composition of newly synthesized proteins were found between the micromeres, which are the most committed cell type, and the macromeres and mesomeres. First, the micromeres lacked triply modified forms of histone H3; the levels of doubly modified forms of H3 were also greatly reduced. In contrast, micromeres were enriched in a band which migrated at the position of unmodified, unacetylated, histone H3 protein. Second, the overall distribution of H2A histone variants differed among the three cell types. Compared with macromeres and mesomeres, micromeres had a higher ratio of alpha-stage to cleavage-stage (CS) histone H2A; the micromere nuclei were depleted by 50 and 35%, respectively, in embryonically synthesized histone CS-H2A. Third, micromeres displayed different profiles of H1 histones. (a) They contained a cleavage-stage H1 histone which migrated faster than that of macromeres and mesomeres. This protein displays the electrophoretic behavior expected for a protein with reduced levels of posttranslational covalent modification. (b) Micromeres also had reduced levels of an H1 histone (designated H1 alpha a) band found in the alpha-H1 region of macromeres and mesomeres. These changes in chromatin modification correlate with the degree of commitment of cells in the developing embryo; they may reflect differing activities of the chromatin modifying enzymes in the various cell types at the 16-cell stage. Thus, the newly synthesized chromatin proteins of the individual blastomere types already differ in the developing sea urchin by the 16-cell stage. We suggest that variations in histone subtypes and in the levels of activity of chromatin modifying enzymes, e.g., acetylases and phosphorylases, could be involved in commitment and differentiation of different cell types.

Acetylation↗
PubMed1984

Histone H3 modification in BHK cells infected with foot-and-mouth disease virus.

Infection of BHK cells with foot-and-mouth disease virus (FMDV) causes a thorough change in the electrophoretic profile of whole nuclear histones. It consists in the disappearance of histone H3 and the appearance of a new polypeptide (Pi) which migrates between histones H2A and H4 on SDS-polyacrylamide gels. Protein Pi is detected at 2 hr postinfection (pi), the time in which viral RNA synthesis begins to increase, and reaches equimolecular amounts with the remaining core histones 1 hr later, when the disappearance of histone H3 is almost complete. Labeling of cells prior to infection demonstrates that Pi is not a novo product but the result of a viral-induced processing of a host precursor synthetized beforehand. Protein Pi comigrates with histone H2A/B in acetic acid/urea polyacrylamide gels and it shares common major peptides with histone H3 under controlled proteolysis with protease V8 or trypsin. The mononucleosomal and nucleosomal DNA pattern analysis after micrococcal nuclease treatment of nuclei from infected and mock-infected cells did not show any significant differences even though after 3 hr (p.i.), protein Pi replaces histone H3 in the nucleosomal structure. It was concluded that FMDV infection is responsible for a specific modification in the nucleus of infected cells which leads, after 3 hr (p.i.), to a complete histone H3 protein Pi transition in the nucleosomes.

Animals↗
PubMed1976

On the existence of polyadenylated histone mRNA in Xenopus laevis oocytes.

In a variety of systems, histone mRNA has been shown to lack poly(A) (Adesnik and Darnell, 1972; Grunstein et al., 1973). We have found, however, that in Xenopus laevis oocytes, poly (A)-containing mRNA codes for histones, in a wheat germ cell-free system, based on the following criteria: first, co-migration with authentic X. laevis oocyte histones on polyacrylamide gels; second, no detectable incorporation of tryptophan; third, differential incorporation of lysine and methionine into histone fraction H2A; fourth, resistance of histone fraction H2A to cleavage with cyanogen bromide; and fifth, correspondence of tryptic peptide maps of partially purified cell-free products with authentic X. laevis oocyte histone. RNA which directs the synthesis of histones in the cell-free system is retained on oligo(dT)-cellulose, even after denaturation in 80% DMSO at 70 degrees C, thereby demonstrating the covalent attachment of polyadenylic acid sequences to the mRNA. Poly (A)- RNA (7S-14S fraction) was also found to code for histones using the same criteria. We discuss the significance of the finding that X. laevis oocytes contain two classes of histone mRNA as well as the potential developmental implications of this observation.

Animals↗
PubMed1978

Studies on histone organization in the nucleosome using formaldehyde as a reversible cross-linking agent.

A new procedure is described which allows selective reversal of formaldehyde cross-linking in both histone-histone and histone-DNA of nuclei isolated from calf thymus. All ten possible dimers of the four non-H1 histones, H3, H2B, H2A and H4, are observed, the major dimers being H3-H3, H3-H2A, H2B-H2A, H2a-H2A and two separate dimers of H2B-H4. Although oligomers of the non-H1 histones are formed by prolonged treatment with this reagent, 50% of the histones continue to remain resistant to cross-linking with each other. For those histones which cross-linking with each other. For those histones which cross-link, the site of cross-linking within the molecules is located in the "core" (trysin-resistant) regionand therfore indicates proximities for these molecules within the nucleosome. The core region also cross-links to DNA, indicating intimate interactions between this region in all the non-H1 histones with DNA.

Binding Sites↗
PubMed1981

Cell-cycle regulation of yeast histone mRNA.

The levels of H2A and H2B mRNAs as a function of cell-cycle stage were determined by hybridization methods. The analysis was extended to H3 and H4 mRNAs by in vitro translation. Cells were partitioned into cell-cycle stages either by centrifugal elutriation or by G1 synchronization with the yeast mating pheromone, alpha factor. The data lead to the following conclusions. First, histone mRNA can be detected in significant quantities only in S-phase cells. Second, the point of maximal accumulation of histone mRNA is not coincident with the point of maximal DNA synthesis; rather, histone mRNA begins accumulating very early in S, reaching a maximum when less than one half of the DNA has replicated. From this point in the cell cycle the histone mRNA levels decrease, reaching basal levels at the end of S. Third, in spite of the fact that the rate of histone mRNA accumulation is not coincident with the rate of DNA synthesis, the two processes are coupled; inhibition of DNA synthesis results in an extremely rapid disappearance of histone mRNA that is much shorter than the normal histone mRNA half-life. Fourth, there is no visible accumulation of mRNA precursors at any cell-cycle stage. We can conclude that, in yeast, histone mRNA levels are tightly and coordinately regulated throughout cell division and that this regulation most likely occurs at both transcriptional and posttranscriptional levels. We also show that the two genetically unlinked H2B genes present in yeast are both expressed at comparable levels and are regulated. The regulation is probably sequence-specific, since genes in close proximity to the histones are not subject to cell-cycle control.

Cell Cycle↗
PubMed1989

Change in the pattern of histone binding to DNA upon transcriptional activation.

Patterns of histone binding to DNA of transcriptionally active D. melanogaster hsp70 genes within the nuclei have been analyzed by two methods of histone-DNA chemical cross-linking. When cross-linking is restricted to the central, "globular" regions of histones, it drops most for H1, to an intermediate extent for H2A and H2B, and least for H3 and H4 in transcriptionally active versus transcriptionally silent chromatin. When it occurs via histone terminal regions as well, cross-linking is quantitatively similar for active and inactive chromatin. Neither cross-linking method detects histones on the hsp70 promoter region. It appears that chromatin activation decreases histone binding to DNA via the "globular" regions, known to be essential for the folding of nucleosomes and the 30 nm chromatin fibril, but does not significantly affect the interaction of flexible and loosely bound histone "tails" with DNA. The role of these histone-DNA interaction changes in the unfolding of active chromatin and RNA polymerase reading through histone-bound DNA is discussed.

Animals↗
PubMed1990

Preparation of fluorescently labelled hybrid histone octamers.

Labelling hybrid histone octamers (the Cys variant of histone H4 replaced histone H4 in the chicken erythrocyte octamer) with the fluorescent probe 5-(2(iodoacetyl)aminoethyl)aminonapthalene- 1-sulfonic acid, IAEDANS, resulted in significant non-specific incorporation of label. Fluorescently labelled hybrid histone octamers were prepared by reconstitution methodology after labelling the isolated histone Cys-H4 and separation of specifically and non-specifically labelled histone. Core particles prepared from these octamers have identical thermal denaturation to unlabelled core particles demonstrating that the incorporation of a fluorescent probe at this site has no overall effect on either histone-histone or histone-DNA interactions. DNase 1 digestion of 32P end-labelled fluorescent core particles yielded the anticipated asymmetric cutting pattern with a 10 bp interval between fragments. Comparison of the cutting pattern with those previously obtained in these laboratories for both polyglutamic acid reconstituted and 'native' core particles demonstrated that fluorescent core particles had an enhanced susceptibility to digestion at site 7.

Amino Acids↗
PubMed1995

Differential compaction of transcriptionally competent and repressed chromatin reconstituted with histone H1 subtypes.

Chromatin fragments stripped of H1 histones regain the ability to form higher order structures and aggregates in 0.15 M NaCl following reconstitution with histone H1. However, transcriptionally competent chromatin fragments are resistant to chicken erythrocyte H1/H5 histone-induced 0.15 M NaCl aggregation/precipitation. In this study, we investigated the ability of stripped chromatin fragments reconstituted with one of four histone H1 subtypes (chicken erythrocyte H1, H5, trout liver H1a, H1b) at various stoichiometries to form salt precipitable higher order structures. Our results provide evidence that chicken erythrocyte histone H1 was more effective than histone H5 and trout liver histone H1b better than H1a in forming higher order structures. None of the histone H1 subtypes could render transcriptionally competent chromatin fragments insoluble in 0.15 M NaCl. These results are consistent with the ideas that the histone H1 subtypes differ in their capacities to compact chromatin fiber, and that the alterations in the structure of transcriptionally competent nucleosomes interfere with the capacity of all H1 subtypes to form higher order structures.

Acetylation↗
PubMed1996

A comparative study of histone deacetylases of plant, fungal and vertebrate cells.

The enzymatic equilibrium of reversible core histone acetylation is maintained by two enzyme activities, histone acetyltransferase and histone deacetylase (HD). These enzyme activities exist as multiple enzyme forms. The present report describes methods to extract different HD-forms from three organisms, germinating maize embryos, the myxomycete Physarum polycephalum, and chicken red blood cells; it provides data on the chromatographic separation and partial purification of HD-forms. In germinating maize embryos three HDs (HD1-A, HD1-B, HD2) can be discriminated; HD1-A, HD1-B, and HD2 were characterized in terms of their dependence on pH, temperature and various ions, as well as kinetic parameters (Km for core histones) and inhibition by various compounds. The same parameters were investigated for the corresponding enzymes of Physarum polycephalum, and mature and immature chicken erythrocytes. Based on these results, optimum assay conditions were established for the different enzyme forms. The kinetic data revealed that the maize histone deacetylase HD1-B peak after partial purification by Q-Sepharose chromatography was heterogeneous and consisted of two histone binding sites that differed significantly in their affinity for purified core histones. Optimized affinity chromatography on poly-Lysine Agarose indeed showed that the former defined deacetylase HD1-B can be separated clearly into two individual HD enzyme forms. The high multiplicity of histone deacetylases underlines the importance of these enzymes for the complex regulation of core histone acetylation.

Acetylation↗
PubMed1996

Prothymosin alpha binds histones in vitro and shows activity in nucleosome assembly assay.

Prothymosin alpha (Pro Talpha) is a polypeptide which appears to be involved in cell proliferation, though its precise function has yet to be identified. Here, we report experiments which show that calf Pro Talpha selectively binds to core histones and histone H1 in vitro. Characterization of these interactions by various procedures (including affinity chromatography on Pro T alpha-Sepharose columns, immunoblotting assay and investigation of the behaviour of mixtures of Pro T alpha and histones in solution) indicated that Pro T alpha has higher affinity for core histones (particularly H3 and H4) than for H1. Similarities between the histone-binding patterns of Pro T alpha and of poly(glutamic acid) suggest that the observed histone-binding capacity resides largely in the acidic central region of Pro T alpha. However, all five histones were also bound by T alpha 1 (a peptide corresponding to the first 28 amino acids of Pro T alpha); histone binding by the N-terminal region of Pro T alpha thus cannot be ruled out. Phosphorylation of Pro T alpha does not appear to affect these interactions. In accordance with the observed capacity for histone binding, Pro T alpha (in conjunction with ATP and some Pro T alpha-binding factor/s in a thymocyte extract) was able to induce in vitro nucleosome assembly. We discuss the possibility that Pro T alpha plays a role in chromatin remodelling.

Amino Acid Sequence↗
PubMed2004

Differential expression of histone post-translational modifications in acute myeloid and chronic lymphocytic leukemia determined by high-pressure liquid chromatography and mass spectrometry.

The post-translational modification of the core histones is critical to the regulation of chromatin structure. Traditional methods for the determination of histone modification utilize immunoassay techniques to determine the extent and site of post-translational modification. These methods, though sensitive, require site-specific antibodies. This manuscript describes the application of reverse-phase high-pressure liquid chromatography and mass spectrometry (LC-MS) to analyze global modification levels of core histones. The method is fast, sensitive, and easily automated. Furthermore, the technique gives the global patterns of modification for all four core histones in a single experiment. The LC-MS method was optimized using histones extracted from bovine thymus. These methods were then applied to the characterization of changes in histone modification in acute myeloid leukemia (AML) cell lines treated with histone deacetylase (HDAC) inhibitors. Dose-dependent changes in the distribution of modified core histones were observed. These results were validated in primary leukemia cells from patients with refractory or relapsed AML or chronic lymphocytic leukemia (CLL) treated on a Phase I clinical trial of the HDAC inhibitor depsipeptide. An increase in the relative abundance of specific acetylated forms of histone H4 was readily observable in these patients at intervals of 4 and 24 h after treatment.

Animals↗
PubMed2006

Histone H1 vaccine therapy for overcoming acute rejection in experimental organ transplantation.

OBJECTIVE: In a rat tolerogenic orthotopic liver transplantation (OLT) model, the recipient serum (post-OLT serum) shows strong immunosuppressive activity. In our previous reports, we suggested that autoreactive antibody (Ab) against histone H1 is a major immunosuppressive factor in this serum. The present study sought to determine whether up-regulation of anti-histone H1 Ab by histone H1 vaccination led to tolerance. MATERIALS AND METHODS: Using mixed lymphocyte reactions (MLR) and heterotopic heart transplantations (HHT), the alloreactive T-cell responses and allograft survivals of histone H1-immunized rats were compared with those of control rats. Cytokine and cellular profiles were determined by enzyme-linked immunosorbent assay (ELISA) and flow cytometry. RESULTS: The alloreactive T-cell response of histone H1-immunized rats was significantly lower than that of control rats, although there was no difference in nonspecific T-cell activation between the 2 groups. The allograft survival of histone H1-immunized rats was significantly prolonged after HHT. The major histocompatibility complex (MHC) class II and CD25 molecules of histone H1-immunized rats were significantly down-regulated compared with those of control rats. Moreover, the serum cytokine profile was modified by the immunization with histone H1. CONCLUSIONS: These results suggest that histone H1 vaccination of transplant recipients leads to the production of immunosuppressive factors and the modification of cytokine/cellular profiles.

Animals↗
PubMed2004

string(cdc25) and cyclin E are required for patterned histone expression at different stages of Drosophila embryonic development.

Metazoan replication-dependent histone mRNAs accumulate to high levels during S phase as a result of an increase in the rate of histone gene transcription, pre-mRNA processing, and mRNA stability at the G1-S transition. However, relatively little is known about the contribution of these processes to histone expression in the cell cycles of early development, which often lack a G1 phase. In post-blastoderm Drosophila embryos, zygotic expression of the stg(cdc25) phosphatase in G2 activates cyclin/cdc2 kinases and triggers mitosis. Here we show that histone transcription initiates in late G2 of cycle 14 in response to stg(cdc25) and in anticipation of S phase of the next cycle, which occurs immediately following mitosis. Mutation of stg(cdc25) arrests cells in G2 and prevents histone transcription. Expression of a mutant form of Cdc2 that bypasses the requirement for stg(cdc25) activates histone transcription during G2 in stg(cdc25) mutant embryos. Thus, in these embryonic cycles, histone transcription is controlled by the principal G2-M regulators, string(cdc25), and cdc2 kinase, rather than solely by regulators of the G1-S transition. After the introduction of G1-S control midway through embryogenesis, histone expression depends on DNA replication and the function of cyclin E, and no longer requires stg(cdc25). Thus, during the altered cell cycles of early animal development, different cell cycle mechanisms are employed to ensure that the production of histones accompanies DNA synthesis.

Animals↗