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Query: UNIPROT:P50583 (asymmetrical)
 12,197 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Electron spin resonance study of Mn (II) binding to chromatin and derivatives, including core particles, shows that Mn (II) is a good probe for testing the overall electrostatic balance of the nucleoproteic complex as well as DNA accessibility. Experimental results are in good agreement with a recent model proposed (Mirzabekov A. D. and Rich A. (1979) Proc. Natl. Acad. Sci. USA 76, 1118-1121), for the core particle, in which an asymmetrical shielding of DNA by the protein core is assumed. Furthermore, it was found that the histone H1 hinders a number of charges on the linker DNA in a proportion equal to the net positive charge of the histone itself. This result is interpreted as due to a tighter interaction between the linker DNA and the core histones in the presence of histone H1.
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PMID:Experimental evidence for asymmetrical shielding of nucleosomal DNA by histones. 23 Apr 66

Heat shock or arsenite treatment alter the pattern of histone methylation in Drosophila cells. Both types of stress induce a rapid increase in the methylation level of histone H2B. The methylated amino acid residue of H2B has been identified by thin layer chromatography and electrophoresis as methylproline and is located at the N-terminal end of H2B. Heat shock also induces a decrease in the level of methylation of histone H3. Under normal growth temperature conditions, histone H3 is shown to be methylated on lysine residues. However under heat shock conditions, there is a decrease in the extent of methylation of lysine residues and the appearance of new methylation on arginine residues in H3. These new heat shock-induced methylated residues have been identified as the symmetrical and asymmetrical forms of dimethylarginine. The methylated amino acid residue of histone H4 is lysine with mono-, di-, and trimethyl forms found in both control and heat or chemically stressed cells. These stress-induced changes in the methylation level of the N-terminal proline residue of histone H2B and shift in the methylation sites of histone H3 may be involved in the restructuration of chromatin accompanying the inactivation of normal genes in response to stress. Moreover, we suggest that the hypermethylation of H2B may also be involved in its protection from increased ubiquitin-mediated proteolytic activity under these conditions of cellular stress.
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PMID:Methylation of Drosophila histones at proline, lysine, and arginine residues during heat shock. 312 88

Rat liver nuclear thyroid hormone receptor was subjected to limited trypsin digestion, and the tryptic fragment of the 3,5,3'-triiodo-L-thyronine (T3)-receptor complex was characterized. Rat liver nuclear thyroid hormone receptor is an asymmetrical protein with Stokes radius of 34 A, sedimentation coefficient of 3.4 S, and molecular weight of 49,000. A globular T3-receptor complex with Stokes radius of 22 A, sedimentation coefficient of 2.8 S, and molecular weight of 26,000 was obtained by tryptic digestion. This fragment had no DNA binding activity, whereas undigested receptor showed significant DNA binding activity. Addition of undigested receptor to the tryptic fragment did not restore DNA binding activity of digested receptor, nor did mixing inhibit DNA binding activity of undigested receptor complex. Undigested receptor bound to core histones, and this activity was stronger than with other proteins tested (H1 histone, cytochrome c, and ovalbumin). The tryptic fragment of receptor maintained core histone binding activity comparable to that of undigested receptor. The tryptic fragment had affinity for T3 comparable to undigested receptor as assessed by Scatchard analysis and the same rate for dissociation of [125I]T3 from receptor. The tryptic fragment of the T3-receptor complex was more stable than undigested receptor at 43 degrees C. Digestion of receptor unoccupied by T3 caused a significantly larger loss of T3 binding capacity than did digestion of T3-occupied receptor, suggesting a protective effect of T3 on a second trypsin-sensitive site on the receptor, which, when cut, destroys T3 binding activity.
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PMID:Separation of DNA binding domain from hormone and core histone binding domains by trypsin digestion of rat liver nuclear thyroid hormone receptor. 378 33

Dinucleosomes purified from micrococcal nuclease digests of steer kidney nuclei were stripped of H1 histone by exposure to 0.50 M NaCl. They were then formed in a complex with individual subfractions of calf thymus H1 histone by dialysis of histone-dinucleosome mixtures from 0.50 M NaCl to concentrations of NaCl between 0 M and 0.08 M; between 0.30 M and 0.10 M the complexes precipitated, and so were not included in the study. The presence of H1 in the complexes was shown to cause an asymmetrical, ordered condensation as revealed by distortions of the circular dichroic spectrum of the DNA. The distortions were negligible at 0.04 M NaCl and below, and increased as a function of ionic strength between 0.05 M and 0.08 M. The degree of distortion of the spectrum, and therefore the nature of dinucleosome condensation, differed greatly from one H1 subfraction to the next. One of the three subfractions tested had almost no effect on the circular dichroism in comparing its dinucleosome complex to H1-depleted dinucleosomes. The other subfractions to different degrees produced large distortions that resulted in spectra that were of the psi type at the higher salt concentration.
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PMID:Condensation of dinucleosomes by individual subfractions of H1 histone. 727 70

We have reconstituted oligonucleosome complexes containing histone H1 starting from a synthetic DNA template, consisting of 12 tandemly arranged 208-base pair fragments of the 5 S rRNA gene, purified HeLa histone octamers, and histone H1. A ratio of histone H1 per histone octamer used in the reconstitution (0.8-0.9 mol of histone H1/mol of histone octamer) similar to that observed in vivo was used. The reconstituted chromatin complexes exhibit a salt-dependent folding, which is almost indistinguishable from that exhibited by chromatin fragments obtained from nuclease digestion of native chromatin. The folding of this reconstituted chromatin complex seems to be rather independent of the symmetrical or asymmetrical position occupied by H1 in the individual nucleosomes. Binding of histone H1 to the oligonucleosome complexes, under the stoichiometric binding conditions used, had no inhibitory effect on the transcriptional potential of these complexes.
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PMID:Folding of chromatin in the presence of heterogeneous histone H1 binding to nucleosomes. 956 81

Increased expression of 5-lipoxygenase is associated with various neuropathologies and may be related to epigenetic gene regulation. DNA methylation in promoter regions is typically associated with gene silencing. We found that human NT2 cells, which differentiate into neuron-like NT2-N cells, express 5-lipoxygenase and we investigated the relationship between 5-lipoxygenase expression and the methylation state of the 5-lipoxygenase core promoter. We used the demethylating agent 5-aza-2'-deoxycytidine and the histone deacetylase inhibitor valproate to alter DNA methylation and to induce histone modifications. 5-Lipoxygenase expression and DNA methylation were assayed with RT-PCR and bisulfite genomic sequencing, respectively. Neuronal differentiation of proliferating NT2 precursors decreased 5-lipoxygenase expression. 5-Aza-2'-deoxycytidine increased 5-lipoxygenase mRNA levels only in proliferating cells, whereas valproate increased 5-lipoxygenase mRNA levels in a cell cycle-independent manner. In both precursors and differentiated cells, CpG dinucleotides of the promoter were poorly methylated. In precursors, both 5-aza-2'-deoxycytidine and valproate further reduced the number of methylated CpGs. Moreover, we found evidence for cytosine methylation in CpWpG (W=adenine or thymine) and other asymmetrical sequences; CpWpG methylation was reduced by valproate in NT2-N but not in NT2 cells. This is the first report demonstrating that the dynamics of DNA methylation relates to neural 5-lipoxygenase gene expression.
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PMID:DNA methylation as an epigenetic regulator of neural 5-lipoxygenase expression: evidence in human NT2 and NT2-N cells. 1500 43

The human T-cell leukemia virus type 1 (HTLV-1) is a retrovirus that integrates randomly into the T-cell genome. Two long terminal repeats (LTRs) flank the integrated provirus. The upstream and downstream LTRs carry identical promoter sequences. Studies with other retroviruses suggest that the downstream promoter is silent and that RNA polymerases initiating at the upstream promoter proceed through the 3' LTR. In this study, we used the chromatin immunoprecipitation assay to compare the binding of transcription regulatory proteins at both the upstream and downstream promoters in HTLV-1-infected cell lines and adult T-cell leukemia-lymphoma cells. Unexpectedly, we detected a nearly equal distribution of activator (Tax, CREB, ATF-1, ATF-2, c-Fos, and c-Jun) and regulatory protein (CBP, p300, TAF(II)250, and polymerase II) binding at both the upstream and downstream promoters. Consistent with this observation, we found that the downstream promoter was transcriptionally active, suggesting that the two promoters are functionally equivalent. We also detected asymmetrical binding of histone deacetylases (HDAC-1, -2, and -3) at both promoters. All three HDACs strongly repressed Tax transactivation, and this repression correlated with displacement of Tax from the HTLV-1 promoter. These effects were reciprocal, as Tax expression reversed HDAC repression and displaced HDACs from the HTLV-1 promoter. These data suggest that HTLV-1 transcriptional regulation at both the 5' and 3' LTRs is mediated, in part, through the mutually exclusive binding of Tax and HDACs at the proviral promoters.
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PMID:Transcription regulatory complexes bind the human T-cell leukemia virus 5' and 3' long terminal repeats to control gene expression. 1522 16

Analysis of the UGA3-GLT1 bidirectional promoter has indicated that its transcriptional activation is determined by the combined action of Gcn4p and Gln3p, and that its bidirectional character is influenced by chromatin organization, through the action of an Abf1p binding site and a polydAdTtract. Results presented in this paper show that lack of Gcn5p impairs histone acetylation and nucleosomal organization of the UGA3-GLT1 promoter, resulting in an asymmetrical transcriptional activation response of UGA3 and GLT1. The phenotype displayed by a double mutant impaired in GCN5 and in the Abf1p binding site indicates that the combined action of these two elements determines the bidirectional capacity of the UGA3-GLT1 intergenic region.
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PMID:Gcn5p contributes to the bidirectional character of the UGA3-GLT1 yeast promoter. 1690 75

Methylation of the lysine 9 residue of histone H3 (H3K9) is linked to transcriptional repression. The observed structure of chromatin in porcine and murine embryos is different with regard to H3K9 dimethylation status, leading to our hypothesis that the intracellular mechanisms responsible for H3K9 methylation would also differ between these two species. The objectives of this study were: (1) to determine the extent that DNA, mRNA, and protein synthesis serve in maintaining the asymmetrical distribution of dimethylated H3K9 in porcine zygotes, (2) determine the extent to which the intracellular localization of individual pronuclei correlated with H3K9 dimethylation status, and (3) to determine the abundance of transcripts encoding the histone methyltransferases, with H3K9 methylation activity, in porcine oocytes and embryos. Our findings are that (1) H3K9 dimethylation status is not affected by DNA replication, transcription, or protein synthesis, (2) the location of a pronucleus does not significantly affect the H3K9 dimethylation status of the chromatin within that pronucleus, and (3) the histone methyltransferases with activity for H3K9 differ in transcript abundance in porcine oocytes and cleavage stage embyros. These results support our hypothesis that there is a difference in intracellular mechanisms affecting dimethylation status of H3K9 between porcine and murine embryos.
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PMID:Global H3K9 dimethylation status is not affected by transcription, translation, or DNA replication in porcine zygotes. 2010 27

Histone H3 trimethylation on lysine 27 is one of the histone modifications associated with chromatin of silenced regions. H3K27me3 labeling is initially asymmetrical between pronuclei in mammalian embryos, and then it is remodeled during early development. However, in mouse embryos obtained after somatic cell nuclear transfer (SCNT), H3K27me3 histones inherited from the somatic female cell and associated with X chromosome inactivation have been reported to escape remodeling. Using immunostaining, we investigated the remodeling of H3K27me3 in Bos taurus embryos obtained after in vitro fertilization (IVF) and SCNT. In this species, transfer-induced chromatin remodeling can be clearly separated from embryonic genome activation (EGA), which occurs at the 8-16-cell stage, and cloning by SCNT is 10 times more successful than in the mouse. In early IVF bovine embryos, dense H3K27me3 labeling was localized in the pericentric heterochromatin as recently described in the mouse. Labeling was however unevenly distributed up to the 8-cell stage, suggesting that the parental genomes partitioned before EGA. In female IVF blastocysts, a somatic-like female profile appeared in 21% of the trophoblast cells. This profile, which had one major nuclear H3K27me3 patch, the putative inactive X chromosome (Xi), was absent in male blastocysts. In contrast, the somatic-like female H3K27me3 profile was observed in the majority of the nuclei of female bovine SCNT embryos before EGA. At the 8-16-cell stage, this profile was transiently replaced by pericentric-like labeling in most nuclei. Immunostaining of mitotic chromosomes suggested that the ratio of H3K27me3 labeling in pericentric heterochromatin vs. euchromatin was then rapidly altered. Finally, Xi-like H3K27me3 staining appeared again in trophoblast cells in female SCNT blastocysts. These results suggest a role for EGA in H3K27me3 remodeling, which affects the heterochromatin inherited from the donor cell or produced during development.
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PMID:Nuclear profiles of H3 histones trimethylated on Lys27 in bovine (Bos taurus) embryos obtained after in vitro fertilization or somatic cell nuclear transfer. 2043 Dec 50


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