Histone-acetylating enzyme of brain

1. Acetylation of histones by an enzyme system derived from rat brain and liver (histone acetylase) was studied by using [1-(14)C]acetyl-CoA as the acetyl group donor. 2. The activity of this enzyme was largely confined to the nucleus. 3. Histone-acetylating activity of cerebral nuclei purified by centrifugation through 1.9m-sucrose was not altered by the presence of the cytoplasmic fraction. 4. Cerebral nuclei from adult rats exhibited greater histone-acetylating activity than did the corresponding preparation from newborn animals. 5. Nuclear acetylating activity was higher in brain than in liver of adult rats but not in newborn animals. 6. The partially purified enzyme from cerebral nuclei, prepared by ammonium sulphate fractionation of an acetone-dried powder, specifically catalysed histone acetylation. 7. Polylysine, protamine, serum albumin and gamma-globulin were not enzymically acetylated by this preparation. 8. Soluble acetylating preparations from both brain and liver nuclei were more active towards arginine-rich F3 and slightly lysine-rich F2a and F2b histone fractions than towards the lysine-rich F1 fraction. 9. Enzymic acetylation of chromatin-bound proteins was much less extensive than that of free histones. 10. The high histone acetylase activity in mature brain may reflect the importance of this process in the genetic control of cerebral function.     

Soluble enzymes of nuclei isolated in sucrose and nonaqueous media; a comparative study

Nuclei of calf thymus and liver and of rat liver were isolated in sucrose media and a number of their properties studied in relation to those of corresponding nuclei isolated in non-aqueous media with a view to determining their capacity to retain soluble components. The best preparations of sucrose nuclei were obtained from calf thymus. Cytochrome oxidase measurements and DNA/N ratios were far less sensitive than microscopic examination as indicators of purity when rat liver and calf thymus nuclei were compared. No satisfactory preparation of calf liver nuclei was obtained, contamination with whole cells having been appreciable; such preparations, nevertheless, could be used to advantage in the tests undertaken. DNA content of thymus nuclei isolated in sucrose was much the same as that of non-aqueous ones, pointing to a retention of soluble protein under aqueous conditions of isolation. That this net retention of protein was not due to the impermeability of the nuclear membrane was shown by the hydrolysis of the DNA upon addition of some crystalline DNAase to a sucrose suspension of nuclei. A comparative study of liver and thymus nuclei isolated in aqueous and non-aqueous media with respect to the soluble enzymes glucose-6-phosphate dehydrogenase, adenosine deaminase, and nucleoside phosphorylase yielded the following results: 1. Lyophilization of sucrose-isolated nuclei and their extraction with the organic solvents used in the non-aqueous procedure did not inactivate any of the enzymes tested. In the case of thymus the reverse was true, there being a marked increase in activity of all the enzymes studied. 2. In thymus, nucleoside phosphorylase and adenosine deaminase were active to approximately the same extent in nuclei isolated by either procedure. Glucose phosphate dehydrogenase alone was more active in sucrose-isolated nuclei, pointing to the possibility of an adsorption of this enzyme. 3. In rat liver nuclei isolated in sucrose, lyophilization and treatment with organic solvents revealed only the presence of some dehydrogenase. 4. The washing out of soluble enzymes was most markedly demonstrated in the case of calf liver. Only traces of the nucleoside enzymes were found in the sucrose-isolated nuclei, and in the case of the dehydrogenase only a half of that present in the non-aqueous nucleus remained. The main conclusions drawn were as follows:— 1. In sucrose media the nuclear membrane is ineffectual in preventing the inward or outward diffusion of protein. 2. The extent to which soluble proteins are retained by a nucleus isolated in sucrose appears to depend upon internal structural factors, such as the concentration of DNA in the nucleus. 3. With respect to determining the composition of nuclei in terms of soluble components, the sucrose isolation procedure is considered to be of indifferent merit and hence invalid for such a type of analysis.     

Specificity of the histone lysine methyltransferases from rat brain chromatin

The histone lysine methyltransferases catalyze the transfer of methyl groups from S-adenosylmethionine to specific epsilon-N-lysine residues in the N-terminal regions of histones H3 and H4. These enzymes are located exclusively within the nucleus and are firmly bound to chromatin. The chromosomal bound enzymes do not methylate free or nonspecifically associated histones, while histones H3 and H4 within newly synthesized chromatin are methylated. These enzymes can be solubilized by limited digestion (10-16%) of chromosomal DNA from rapidly proliferating rat brain chromatin with micrococcal nuclease. Histone H3 lysine methyltransferase remained associated with a short DNA fragment throughout purification. Dissociation of the enzyme from the DNA fragment with DNAase digestion resulted in complete loss of enzyme activity; however, when this enzyme remained associated with DNA it was quite stable. Activity of the dissociated enzyme could not be restored upon the addition of sheared calf thymus or Escherichia coli DNA. Histone H3 lysine methyltransferase was found to methylate lysine residues in chromosomal bound or soluble histone H3, while H3 associated with mature nucleosomes was not methylated. The histone H4 lysine methyltransferase which was detectable in the crude nuclease digest was extremely labile, losing all activity upon further purification. We isolated a methyltransferase by DEAE-cellulose chromatography, which would transfer methyl groups to arginine residues in soluble histone H4. However, this enzyme would not methylate nucleosomal or chromosomal bound histone H4, nor were methylated arginine nucleosomal or chromosomal bound histone H4, nor were methylated arginine residues detectable upon incubating intact nuclei or chromatin with S-adenosylmethionine.     

In vitro phosphorylation of chicken erythrocyte histone by various protein kinases : Absence of phosphorylation from F1 histone

In spite of the presence of nucleus, genetic activity and mitosis are totally depressed in avian erythrocytes. If phosphorylation of histone is involved in such genetic depression, a comparative study of phosphorylation of avian erythrocyte histone can be expected to furnish information about the mechanism of gene control. The present study is the examination of susceptibility of chicken erythrocyte histone to histologically different (liver and muscle) and phylogenically different (avian, mammalian and ichthic) protein kinases. It was found that chicken erythrocyte F1 histone was phosphorylated not only by heterologous (rat and trout liver) but also by homologous (chicken liver and muscle) protein kinases. Addition of cAMP could not elicit phosphorylation of this histone, while phosphorylation of other histones was significantly enhanced by this drug. Avian erythrocyte-specific histone, F2c, was markedly phosphorylated not only by avian enzymes but also by mammalian enzyme. All the enzymes tested phosphorylated F2b histone. F3 histone was phosphorylated at least by avian and mammalian enzymes. F2a1 and F2a2 histones were poor substrate to all the enzymes tested.     

Kinetics of accumulation and depletion of soluble newly synthesized histone in the reciprocal regulation of histone and DNA synthesis

Procedures are presented which permit the identification and analysis of cellular histone that is not bound to chromatin. This histone, called soluble histone, could be distinguished from that bound to chromatin by the state of H4 modification and the lack of H2A ubiquitination. Changes in the levels of newly synthesized soluble histone were analyzed with respect to the balance between histone and DNA synthesis in hamster ovary cells. Pulse-chase protocols suggested that the chase of newly synthesized histone from the soluble fraction into chromatin may have two kinetic components with half-depletion times of about 1 and 40 min. When protein synthesis was inhibited, the pulse-chase kinetics of newly synthesized histone from the solubl fraction into chromatin were not significantly altered from those of the control. However, in contrast to the control, when protein synthesis was inhibited, DNA synthesis was also inhibited with kinetics similar to those of the chase of newly synthesized histone from the soluble fraction. There was a rapid decrease in the rate of DNA synthesis with a half-deceleration time of 1 min down to about 30% of the control rate, followed by a slower decrease with an approximate half-deceleration time of 40 min. When DNA synthesis was inhibited, newly synthesized histone accumulated in the soluble fraction, but H2A and H2B continued to complex with chromatin at a significant rate. Soluble histone in G1 cells showed the same differential partitioning of H4/H3 and H2A/H2B between the soluble and chromatin-bound fractions as was found in cycling cells with inhibited DNA synthesis. These results support a unified model of reciprocal regulatory mechanisms between histone and DNA synthesis in the assembly of chromatin.     

Enzymic acetylation of nucleosome histone.

Rat liver chromatin prepared from purified nuclei catalyzed the acetylation of histones in nucleosomes at the same level as that of nuclei. The activity of histone acetyltransferase in chromatin was destroyed by heat treatment at 65 degrees C for 5 min. Histones in exogenously added nucleosomes also served as substrate for the enzyme. The sites of acetylation in the nucleosomes appeared to be in the trypsin-digestable N-terminal regions of histones H4, H3, and H2A, as has been reported in an in vivo system.     

Replacement of protamine by F1 histone during reactivation of fused human sperm nuclei.

Rabbit antisera, specific for the histones F1, F2a2, F2b, F3 and for protamine were used to monitor a possible transition from protamine towards somatic-type histones during sperm nucleus reactivation, following human sperm fusion with mouse fibroblasts. Mature human sperm nuclei were shown to contain the histones F2a2, F2b, F3 and protamine, but were missing F1 histone by immuno cytochemistry using the indirect fluorescence method. However, a gradual disappearance of protamine from fused sperm nuclei, could be observed during the first 24 h of reactivation. Subsequently, F1 histone could be detected in increasing concentrations in 60% of reactivated sperm nuclei, during the next four days. The shift from protamine towards F1 histone could also be visualized cytochemically via staining with brilliant sulphaflavine, which appears to discriminate between sperm nuclei on the basis of their F1 histone content.     

Calcium-activated, phospholipid-dependent protein kinases from rat liver: subcellular distribution, purification, and characterization of multiple forms

Three forms of Ca2+- and phospholipid-dependent protein kinase (protein kinase C) were extensively purified from rat liver homogenate. Subcellular fractionation analysis indicated that the majority (approximately 85%) of the activity was associated with particulate fractions of the liver. Among these, the microsomal and nuclear fractions accounted for approximately 63% and approximately 10% of total activity. The remaining 15% of protein kinase C was recovered in the soluble fraction following differential centrifugation. It was also found that most of the membrane-associated protein kinase C was latent, with 4-6-fold stimulation with detergents such as 3-[(3-cholamidopropyl)dimethylammonio]-2-hydroxy-1-propanesulfonate, octyl beta-glucoside, or Triton X-100. The activity of both the bound form and the soluble enzyme was enhanced by the addition of Ca2+ and phosphatidylserine, when histone H1 was used as substrate. The bound protein kinase C activity was dissociated by homogenization of liver in buffer containing ethylene glycol bis(beta-aminoethyl ether)-N,-N,N',N'-tetraacetic acid, ethylenediaminetetraacetic acid, and various proteolytic inhibitors, and the solubilized extract was used to purify multiple forms of the enzyme. The purification procedure sequentially utilized (NH4)2SO4 fractionation, ion-exchange chromatography on DEAE-cellulose, gel permeation chromatography on Fractogel TSK HW-55 (F), ion-exchange chromatography on hydroxylapatite, gel permeation chromatography on Ultrogel AcA34, and affinity chromatography on polyacrylamide-immobilized phosphatidylserine. On hydroxylapatite columns, protein kinase C activity was resolved into three isoenzymic forms designated C-I, C-II, and C-III. The molecular weights of the three isoenzymic forms were in the range of 208,000-225,000 as shown by chromatography on calibrated Ultrogel AcA34 columns and sucrose density gradient centrifugation. Furthermore, all three isoenzymes demonstrated a single peak with a sedimentation coefficient (s20.w) in the range of 9.0-9.2. However, with polyacrylamide gel electrophoresis, all the forms showed a single protein component with average molecular weight of 64K, suggesting that the native isoenzymes may be composed by subunits. Finally, all three isoenzymes exhibited nearly identical enzymatic properties.     

Replacement of protamine by F1 histone during reactivation of fused human sperm nuclei

Summary Rabbit antisera, specific for the histones F1, F2a2, F2b, F3 and for protamine were used to monitor a possible transition from protamine towards somatic-type histones during sperm nucleus reactivation, following human sperm fusion with mouse fibroblasts.Mature human sperm nuclei were shown to contain the histones F2a2, F2b, F3 and protamine, but were missing F1 histone by immuno cytochemistry using the indirect fluorescence method. However, a gradual disappearance of protamine from fused sperm nuclei, could be observed during the first 24 h of reactivation. Subsequently, F1 histone could be detected in increasing concentrations in 60% of reactivated sperm nuclei, during the next four days.The shift from protamine towards F1 histone could also be visualized cytochemically via staining with brilliant sulphaflavine, which appears to discriminate between sperm nuclei on the basis of their F1 histone content.     

Histone kinase and cell division

1. The activity of the soluble phosphokinase for histone F1 increases in regenerating rat liver during the first period of DNA synthesis after partial hepatectomy. The increase probably represents new enzyme synthesis. 2. A dose of 500rd of gamma-irradiation given early in G1 decreases the amount of histone F1 phosphokinase found 22h after partial hepatectomy by 60-70%. 3. The enzyme preparations also contained a histone F1 phosphatase; the presence together of the kinase and phosphatase caused a disproportion between net (31)P uptake and (32)P incorporation into histone F1. 4. All four subclasses of histone F1 could accept phosphate from ATP. 5. Crude enzyme preparations transferred more (31)P into histone F1 with an initially low phosphate content than into one with a high phosphate content; conversely, more (32)P was transferred into the latter.     

THE ENZYMIC HYDROLYSIS OF PHOSPHATIDYL INOSITOL BY GUINEA PIG BRAIN:

Abstract—

• 1 Phosphatidylinositol hydrolase activity of homogenates of guinea pig brain was studied by using [2-³H]inositol labelled substrate and measuring the release of radioactivity into the acid soluble fraction.
• 2 Inositol phosphate and diglyceride were found to be the main hydrolysis products. The principal enzyme involved, therefore, is a phosphatidylinositol inositolphosphohydrolase.
• 3 Most of the enzymic activity (61 per cent) was found in the soluble fraction. Osmotic shock of the high speed particulate fraction resulted in release of an additional 23 1 per cent into the soluble fraction. However, as contrasted to lactate dehydrogenase, significant activity remained particulate bound.

     

The isolation of cell nuclei in non-aqueous media

1. A modified Behrens procedure is described for the isolation of nuclei from avian erythrocytes and from the liver, kidney, thymus, pancreas, heart, and intestinal mucosa of the calf or horse. 2. The purity of these nuclei has been established by staining reactions, enzyme studies, and immunological tests for serum proteins. 3. Evidence is presented to show that a transport of cytoplasmic proteins into the nucleus does not occur during the isolation. 4. Nuclei prepared in non-aqueous media contain considerably more protein and a very different enzyme composition from that observed in nuclei prepared by "homogenization" techniques in dilute citric acid. 5. The suitability of nuclei prepared in organic media for the study of intracellular enzyme distribution is discussed.     

Site specificity of yeast histone acetyltransferase B complex in vivo

Saccharomyces cerevisiae Hat1, together with Hat2 and Hif1, forms the histone acetyltransferase B (HAT-B) complex. Previous studies performed with synthetic N-terminal histone H4 peptides found that whereas the HAT-B complex acetylates only Lys12, recombinant Hat1 is able to modify Lys12 and Lys5. Here we demonstrate that both Lys12 and Lys5 of soluble, non-chromatin-bound histone H4 are in vivo targets of acetylation for the yeast HAT-B enzyme. Moreover, coimmunoprecipitation assays revealed that Lys12/Lys5-acetylated histone H4 is bound to the HAT-B complex in the soluble cell fraction. Both Hat1 and Hat2, but not Hif1, are required for the Lys12/Lys5-specific acetylation and for histone H4 binding. HAT-B-dependent acetylation of histone H4 was detected in the soluble fraction of cells at distinct cell cycle stages, and increased when cells accumulated excess histones. Strikingly, histone H3 was not found in any of the immunoprecipitates obtained with the different components of the HAT-B enzyme, indicating the possibility that histone H3 is not together with histone H4 in this complex. Finally, the exchange of Lys for Arg at position 12 of histone H4 did not interfere with histone H4 association with the complex, but prevented acetylation on Lys5 by the HAT-B enzyme, in vivo as well as in vitro.     

Lactate dehydrogenase activity in the mitochondrial fraction of chicken liver: enzyme binding and kinetic behavior of soluble and bound enzyme

Chicken liver crude mitochondrial fraction showed lactate dehydrogenase activity (6.5% of cytoplasmic enzyme). Most of the mitochondrial lactate dehydrogenase was solubilized by sonication of the mitochondrial fraction in 0.15 M NaCl, pH 6. Total extracted lactate deshydrogenase activity was 3-fold higher than the initial pellet activity. Different isoenzymatic compositions were observed for cytosoluble and mitochondrial extracted lactate dehydrogenase. The pI, values of the 5 lactate dehydrogenase isoenzymes were found to be independent of their origin. The cytosoluble lactate dehydrogenase and the separated H4,H3M and H2M2 isoenzymes were able to bind to the chicken liver mitochondrial fraction in 5 mM sodium phosphate buffered medium, and could be solubilized afterwards with 0.15 M NaCl, pH 6. The enzyme bound to the mitochondrial fraction was less active than the soluble one. Particle saturation by the bound enzyme occurred with all mitochondrial fractions assayed. According to the Langmuir isotherm, the non-sonicated mitochondrial fractions contain a single type of binding sites for lactate dehydrogenase; in contrast, the sonicated mitochondrial fraction should contain different binding sites. Chicken liver crude or sonicated active mitochondrial fractions showed a hyperbolic behavior with respect to NADH and a non-hyperbolic one with respect to pyruvate. This mechanism is different from the bi-bi compulsory order mechanism of the soluble enzyme. With hydroxypyruvate as the substrate, the active mitochondrial fraction fit a sequential mechanism but lost the rapid-equilibrium characteristics of the soluble enzyme.     

Comparative subcellular distribution of apyrase from animal and plant sources. Characterization of microsomal apyrase

1. Apyrase (ATP: diphosphohydrolase) has been found in the microsomal fraction of rat salivary gland, mammary gland and uterus. 2. This enzyme, already described in plant tissue, is mainly present as a soluble polypeptide in tubers of Solanum tuberosum. 3. A fraction of this enzyme is associated with the microsomal fraction with a higher specific activity than the soluble one, for either ATP or ADP as substrate. 4. Apyrase bound to microsomes from rat and potato tissues was characterized in its substrate specificity and effect of inhibitors. 5. The Km values for ATP and ADP, optimum pH and metal ion requirement were determined. 6. A characteristic common to the microsomal and soluble apyrases is the stimulatory effect of a potato activator protein of soluble plant apyrase. 7. The microsomal-bound apyrase from rat and potato tissues were solubilized and subjected to size-exclusion chromatography. 8. The mammary gland and salivary gland apyrases eluted as molecular aggregates, in contrast to the uterus and potato enzyme.     

Initiation of DNA synthesis in mouse 3T3 fibroblasts in response to a specific factor.

Antibodies specific for both the F 1 and F 2a-1 calf thymus histone fractions were prepared by use of highly purified histone fractions. With these antibodies, immunofluorescent studies were performed in cultured cells from a Syrian hamster, from human cancer and from rat embryonal cells. Specific staining of nuclei by both of the antibodies was seen in all the cell lines used. In the staining pattern of the cell nucleus, there was a distinct difference between the results obtained from anti-F 1 antibody and from anti-F2a-1 antibody. In the case of the anti-F 1, the nuclei were stained to be coarse-grained or clumped in appearance. However, the result from anti-F 2a-1 showed strong fluorescence in the peripheral part of the nucleus and a faint shaggy appearance in the central part of the nucleus. These differences in the nuclear fluorescent pattern between the results obtained from anti-F 1 antibody and from anti-F 2a-1 antibody were seen in all the cell lines used.     

A novel yeast histone deacetylase: partial characterization and development of an activity assay

We have characterized a histone deacetylase activity associated with yeast nuclei. An unusual feature of the deacetylase is that it is not inhibited by the short-chain fatty acids n-butyrate and propionate. These short-chain fatty acids are typically potent inhibitors of histone deacetylases in eukaryotic systems. The deacetylase(s) were detected by monitoring the levels of acetylation of yeast histones during incubation of isolated yeast nuclei. The activity was optimal at 37 degrees C and at 0.1 M NaCl. The enzyme did not require divalent cations and was inhibited by Zn2+ and Cu2+. A simple activity assay was developed using as substrate, [3H]acetate-labeled histone in chicken erythrocyte nuclei. This assay was used to demonstrate that the deacetylase(s) can be extracted from yeast nuclei with 0.5 M NaCl. A gel electrophoretic analysis of the deacetylated chicken histones verified that the solubilization of incorporated radiolabel was a result of histone deacetylation, not an artifact of histone degradation by yeast proteinases.     

Measurement of poly(ADP-ribose) glycohydrolase activity by high resolution polyacrylamide gel electrophoresis: Specific inhibition by histones and nuclear matrix proteins

We have developed a novel enzyme assay that allows the simultaneous determination of noncovalent interactions of poly(ADP-ribose) with nuclear proteins as well as poly(ADP-ribose) glycohydrolase (PARG) activity by high resolution polyacrylamide gel electrophoresis. ADP-ribose chains between 2 and 70 residues in size were enzymatically synthesized with pure poly(ADP-ribose) polymerase (PARP) and were purified by affinity chromatography on a boronate resin following alkaline release from protein. This preparation of polymers of ADP-ribose was used as the enzyme substrate for purified PARG. We also obtained the nuclear matrix fraction from rat liver nuclei and measured the enzyme activity of purified PARG in the presence or absence of either histone proteins or nuclear matrix proteins. Both resulted in a marked inhibition of PARG activity as determined by the decrease in the formation of monomeric ADP-ribose. The inhibition of PARG was presumably due to the non-covalent interactions of these proteins with free ADP-ribose polymers. Thus, the presence of histone and nuclear matrix proteins should be taken into consideration when measuring PARG activity.     

Presence and androgen control of an alkaline phosphatase in the nucleus of rat ventral prostate.

The presence of alkaline phosphatase (EC 3.1.3.1) activity has been demonstrated in nuclei of rat ventral prostate. This enzyme activity remained after washing of isolated nuclei with 0.5% Triton X-100; an acid phosphatase initially present with the nuclear fraction was removed by this treatment. The nuclear alkaline phosphatase, examined by utilizing p-nitrophenyl phosphate as substrate, had a pH optimum of 9.5-10.3, and a broad substrate specificity: p-nitrophenyl phosphate greater than phosphothreonine greater than beta-glycerophosphate greater than phosphoserine. The nuclear phosphatase was sensitive to denaturation by heat or urea treatments and was also inhibited by Pi, L-phenylalanine, homoarginine, dithiothreitol, and EDTA. The EDTA-inhibited enzyme was maximally reactivated by Zn2+, although Mg2+, or Ca2+ were also effective at somewhat higher concentrations. Orchiectomy of adult rats resulted in an increase in the nuclear alkaline phosphatase activity (2-3-fold at 24 or 48 h postorchiectomy). A decline in the protein: DNA ratio also occurred following orchiectomy, but the increase in phosphatase specific activity was evident whether expressed per unit of protein or per unit of DNA. Testosterone replacement following orchiectomy abolished the increase in nuclear phosphatase activity. The results suggest that the prostatic nuclear alkaline phosphatase may be involved in events related to inactivation of the prostate nucleus following androgen deprivation.