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Query: EC:3.1.31.1 (micrococcal nuclease)
 2,818 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The capacity for 3' processing of the histone H4 pre-mRNA is lost following differentiation of rat L6 myoblasts to myotubes. Nuclear extracts prepared from proliferating myoblasts, but not differentiated myotubes, actively process histone H4 pre-mRNA in vitro. The activity of two factors required for 3' processing, the heat-labile factor and U7 snRNP, also changes during the differentiation period, concurrent with the loss of 3' processing activity. During myotube formation, the activity of the heat-labile factor decreases significantly while the 5' sequences of the U7 snRNA become progressively resistant to micrococcal nuclease digestion. Thus, the dramatic down-shift in histone H4 mRNA levels which occurs during myoblast differentiation is controlled at both the transcriptional and posttranscriptional level.
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PMID:Histone H4 mRNA levels are down-regulated by 3' RNA processing during terminal differentiation of myoblasts. 161 Aug 93

Poly(ADP-ribosylation) of histones and several other nuclear proteins seem to participate in nuclear processes involving DNA strand breaks like repair, replication, or recombination. This is suggested from the fact that the enzyme poly(ADP-ribose) polymerase responsible for this modification is activated by DNA strand breaks produced in these nuclear processes. In this article I provide three lines of evidence supporting the idea that histone poly(ADP-ribosylation) is involved in chromatin replication. First, cellular lysates from rapidly dividing mouse or human cells in culture synthesize a significant number of oligo- in addition to mono(ADP-ribosylated) histones. Blocking the cells by treatment of cultures with 5 mM butyrate for 24 h or by serum or nutrient depletion results in the synthesis of only mono- but not of oligo(ADP-ribosylated) histones under the same conditions. Thus, the presence of oligo(ADP-ribosylated) histones is related to cell proliferation. Second, cellular lysates or nuclei isolated under mild conditions in the presence of spermine and spermidine and devoid of DNA strand breaks mainly synthesize mono(ADP-ribosylated) histones; introduction of a small number of cuts by DNase I or micrococcal nuclease results in a dramatic increase in the length of poly(ADP-ribose) attached to histones presumably by activation of poly(ADP-ribose) polymerase. Free ends of DNA that could stimulate poly(ADP-ribosylation) of histones are present at the replication fork. Third, putatively acetylated species of histone H4 are more frequently ADP-ribosylated than nonacetylated H4; the number of ADP-ribose groups on histone H4 was found to be equal or exceed by one the number of acetyl groups on this molecule. Since one recognized role of tetraacetylated H4 is its participation in the assembly of new nucleosomes, oligo(ADP-ribosylation) of H4 (and by extension of other histones) may function in new nucleosome formation. Based on these results I propose that poly(ADP-ribosylated) histones are employed for the assembly of histone complexes and their deposition on DNA during replication. Modified histones arise at the replication fork by activation of poly(ADP-ribose) polymerase by unligated Okazaki fragments.
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PMID:Poly(ADP-ribosylated) histones in chromatin replication. 238 72

Chromatin fractions from Friend erythroleukemia cells after induction of differentiation by dimethylsulfoxide (DMSO) were compared in their biochemical characteristics to fractions from uninduced cells. Fractions were prepared by extracting chromatin from nuclei after mild micrococcal nuclease treatment with increasing concentrations of NaCl according to Sanders. This procedure has been found to release chromatin containing hyperacetylated histones preferentially. The fractions obtained by this procedure were analysed in respect to the amount of chromatin released, the amount of histone H1, the degree of acetylation of histone H4, the presence of non-histone proteins and the concentration of transcribed and non-transcribed sequences. It was found that the fractions differ in the amount of histone H1 present, in several non-histone proteins and in the acetylation of histone H4, regardless whether induced or uninduced cells were analysed. The distribution of transcribed sequences versus non-transcribed sequences among the fractions was the same, demonstrating that this fractionation procedure, although leading to fractions with biochemical differences, is not able to discriminate functional states of chromatin and that the biochemical characteristics of the fractions may be common to both, active as well as inactive states of chromatin.
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PMID:Biochemical characterization of chromatin fractions isolated from induced and uninduced Friend erythroleukemia cells. 257 Oct 75

We have previously constructed a yeast strain (UKY403) whose sole histone H4 gene is under control of the GAL1 promoter. This yeast arrests in G2 upon glucose treatment as a result of histone H4 depletion. The yeast PHO5 gene contains phase nucleosomes covering promoter (UAS) sequences in the PHO5 repressed state and it has been suggested that nucleosomes prevent the binding of positively acting factors to these UAS sequences. Using UKY403 we examined the length of polynucleosomes and nucleosome phasing in the PHO5 upstream region by the use of micrococcal nuclease and indirect end-labeling. It was found that glucose arrest led to a severe disruption in PHO5 chromatin structure and that most nucleosomes had their position altered or were lost from the PHO5 promoter region. Cell undergoing nucleosome depletion synthesized large quantities of accurate PHO5 transcripts even under repressive, high inorganic phosphate conditions. Histone H4 depletion did not appear to affect the repression or activation of another inducible yeast gene, CUP1. Arrest with landmarks in early G1 (in the cell division cycle mutant cdc28) or in various stages of G2 (in cdc15, cdc17 and cdc20) does not activate PHO5; nor does arrest due to chromosome topology changes (in top2 or the top1top2 topoisomerase mutants). cdc14, which has its arrest landmark at a similar point in the cell cycle as cdc15, does derepress PHO5. However, since it also leads to derepression of CUP1 it is probably functioning through an independent mechanism. Therefore, our data suggest that nucleosomes regulate PHO5 transcription.
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PMID:Depletion of histone H4 and nucleosomes activates the PHO5 gene in Saccharomyces cerevisiae. 304 34

The chromatin-bound histone deacetylase of Chinese hamster ovary cells has been studied by using as a substrate an acetylated amino-terminal peptide of histone H4. These studies demonstrate that histone deacetylase activity is associated with mononucleosomes solubilized by digestion with micrococcal nuclease. The deacetylase activity remained bound to the nucleosomes, even in the presence of 1 M NaCl. This unique class of deacetylase-associated mononucleosomes is resolved from the major classes of mononucleosomes by polyacrylamide gel electrophoresis. These mononucleosomes contain 290 and 190 base pair DNAs and demonstrate the presence of histone H1 and non-histones HMG-1 and HMG-2 and the absence of HMG-14 and HMG-17. They are further characterized by a specific acetylation pattern of histone H4 and likely represent a functionally important chromatin-DNA complex.
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PMID:A Chinese hamster ovary cell histone deacetylase that is associated with a unique class of mononucleosomes. 344 54

The organization of nucleosomes associated with a cell cycle regulated human H4 histone gene was examined in synchronized HeLa S3 cells. At various times during the cell cycle, nuclei were digested with micrococcal nuclease, and the nucleosomal pattern of the gene was obtained by Southern blot analysis using radiolabeled human histone H4 gene probes. We have detected reversible changes during the cell cycle in the chromatin structure of this gene, as reflected by the shortening of the nucleosomal spacing after replication and the peak of transcription. This variation is also observed when DNA and protein syntheses are inhibited. By using a probe that comprises 250 base pairs (bp) of the coding region and 240 bp of the 5' end of the gene, containing the promoter and DNase I sensitive sequences, we also have observed a general disruption of the nucleosomal organization, which is reflected by a degeneration of the characteristic nucleosomal ladder produced by micrococcal nuclease digestion. This modification coincides with the replication and active transcription of the gene (early S phase), which recovers its regular nucleosomal appearance when both processes have been completed, although the nucleosome linker length is shortened. When the probe utilized comprises the distal 3' end of the gene, there is no disruption of the nucleosomal pattern, but the linker region also exhibits a shortened length. A non-cell cycle regulated gene (beta-globin) does not exhibit such modifications in any of the situations analyzed.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Reversible changes in the nucleosomal organization of a human H4 histone gene during the cell cycle. 377 65

The relationship between chromatin structure and the transcriptional activity of the histone H4-I gene of Tetrahymena thermophila was explored. Indirect end-labeling studies demonstrated that major DNase I- and micrococcal nuclease-hypersensitive sites flank the active macronuclear genes but not the inactive micronuclear genes. Runon transcription experiments with isolated macronuclei indicated that histone gene transcription rates decreased when cells were starved. However, macronuclear nuclease-hypersensitive sites persisted upon starvation. Thus, one level of transcriptional control of the H4-I gene results in altered chromatin structure and is established during nuclear differentiation. The rate of transcription is also controlled, but not through hypersensitive site-associated structures.
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PMID:Formation of stable chromatin structures on the histone H4 gene during differentiation in Tetrahymena thermophila. 378 21

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.
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PMID:Specificity of the histone lysine methyltransferases from rat brain chromatin. 393 70

A cloned histone H4 gene of Xenopus laevis is efficiently transcribed after injection into germinal vesicles of X. laevis oocytes. Deletion analyses indicate that less than 140 base-pairs of 5' flanking sequences and 50 base-pairs of 3' flanking sequences are required for efficient transcription of this gene in Xenopus oocytes. Chromatin footprint analysis by a direct end-label technique reveals discrete DNase I-hypersensitive and micrococcal nuclease-hypersensitive sites at the 5' and 3' boundaries of the gene, which bracket the transcribed region of this minichromosome. The specific chromatin structure assembled around this homologous gene, together with the finding that histone genes of Drosophila melanogaster are not assembled into specific nucleoprotein structures within Xenopus oocytes, strongly suggest that sequence-specific and species-specific factors may be responsible for generating the chromatin-specific hypersensitive sites at the boundaries of active genes.
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PMID:Chromatin-specific hypersensitive sites are assembled on a Xenopus histone gene injected into Xenopus oocytes. 403 7

During digestion of deoxyribonucleoproteins (DNP) of gram-negative bacteria by micrococcal nuclease and Ca2+, Mg2+-dependent endonuclease in situ regular series fragments-and large nuclease-resistent fragments of DNP were revealed by electrophoresis. The DNP length of the smallest DNP-fragment was tentatively 120-140 base pairs. In investigated bacterial species DNP contained at least two basic proteins which had electrophoretic mobility similar to that of histone H4 of eucaryot. It is suggested that bacterial DNPs have common regular structure.
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PMID:[Probing the structure of bacterial deoxyribonucleoproteins with exogenous and endogenous nucleases]. 624 43


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