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Query: HUMANGGP:040116 (histone)
 44,835 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Alterations in the structure and molecular composition of avian hepatocyte nuclei were compared following administration in vivo of lethal and sub-lethal doses of alpha-amanitin. This toxin interferes with extranucleolar transcription by direct inhibition of RNA polymerase II activity. the resultant effects include: extensive condensation of chromatin, displacement of nucleoplasmic contents and fragmentation of nucleoli. Changes in nuclear morphology were quantitated by stereometry and related to variations in RNA and residual, non-histone proteins (NHP). Gross alterations in nuclear structure and depletion of RNA and NHP levels were of similar magnitude with both doses of amanitin. The effects were fully reversible, however, with a minimal dose but terminal with a lethal dose. DNA and histone protein levels remained unchanged at all stages. These results imply that the process of transciption may itself keep and/or maintain chromatin in a dispersed state, and that in the absence of transcription chromatin naturally condenses. Modification of nuclear proteins may be necessary only to maintain chromatin compacted permanently or for extended periods of time. A model of nuclear organization is proposed to incorporate these considerations and to identify the probable location of the nuclear matrix in situ.
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PMID:The organization, composition and matrix of hepatocyte nuclei exposed to alpha-amanitin. 9 80

The activity of purified RNA polymerase II from Novikoff ascites tumor cells is stimulated 5-7-fold by a purified protein factor. This protein factor, designated HLF2, has extensive protein kinase activity and catalyzed the incorporation of gamma-32G from ATP into protein under normal RNA polymerase assay conditions. Protein phosphorylation is totally dependent on the presence of HLF2 and is stimulated 2-3-fold by the presence of highly purified RNA polymerase II. The purification procedure developed for the isolation of the polymerase stimulatory factor resulted in a 4000-fold purification of a protein kinase. Chromatography on carboxymethylcellulose, phosphocellulose, and Sephadex G-100 did not resolve polymerase stimulatory activity from protein kinase activity. Adenylimidodiphosphate (AMP-PNP), an inhibitor of protein kinases, inhibited the stimulatory activity of purified factor by 80%. The heat denaturation profile of protein kinase was paralleled by the loss of polymerase stimulatory activity. Concentrations of (NH4)2SO4 which are known to inhibit polymerase stimulation (Lee and Dahmus, 1973) also inhibit protein kinase activity. The protein kinase activity associated with stimulatory factor catalyzes the phosphorylation of basic proteins such as protamine or histone. The protein kinase is not stimulated by cyclic 3', 5'-AMP or -GMP over a concentration range of 10(-6)-10(-4)M. Furthermore, protein kinase activity is not inhibited by either the regulatory subunit of rabbit muscle protein kinase or by the heat-stable inhibitor of cyclic 3', 5'-AMP-dependent protein kinases. Protein kinase activity is stimulated by KCl or NH4Cl and is inhibited by MnCl2. The apparent Km values, determined in the presence of 4 mM Mg2+, are 0.02 mM for ATP, and 4.1 mM for GTP.
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PMID:Stimulation of ascites tumor RNA polymerase II by protein kinase. 17 56

The integrity and stability of nucleosomes under transcription assay conditions has been found to depend on concentration and ionic environment. Rifamycin AF/013, a commonly used inhibitor of initiation, is particularly effective in destabilisation of nucleosomes. Intact nucleosomes are refractory to transcription by wheat RNA polymerase II, the histone core preventing initiation. Template titration suggests that the polymerase can, however, bind to nucleosomes, and a 15--16S complex has been observed on sucrose gradients. DNase I digestion of polymerase-nucleosome incubations indicates that whilst histone is still present in the complex, the nucleosome conformation is altered resulting in enhanced nucleolysis at sites near the DNA centre but reduced overall kinetics of digestion.
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PMID:The nature of the interaction of nucleosomes with a eukaryotic RNA polymerase II. 49 50

Nuclei were isolated from synchronized HeLa S3 cells and transcribed utilizing their endogenous RNA polymerases. Our data suggest that S phase nuclei are capable of synthesizing histone mRNA sequences while nuclei from G1 phase cells are not. Transcription of histone mRNA sequences by S phase nuclei can be abolished completely by low levels of alpha-amanitin (1.0 microgram/ml, a concentration which completely inhibits RNA polymerase II). From these results it appears that transcription of the histone mRNA sequences occurs during the S phase but not during the G1 phase of the cell cycle and that RNA polymerase II is responsible for histone gene readout.
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PMID:Synthesis of histone messenger RNAs by RNA polymerase II in nuclei from S phase HeLa S3 cells. 66 92

RNA transcribed in isolated sea urchin nuclei and assayed by hybridization to histone genes cloned in E. coli contains sequences homologous to each of the five histone genes. Histone RNA is synthesized exclusively from the same DNA strand which is the template in vivo. Synthesis of the histone gene transcripts is sensitive to alpha-amanitin concentrations which inhibit RNA polymerase II activity. The fraction of histone RNA synthesized in vitro is comparable at two developmental stages to the fraction synthesized in vivo. The nuclear histone transcripts contain sequences homologous to spacer DNA regions present between the coding regions of the 6500 base pair (bp) histone gene repeat unit. The transcription of spacer sequences was demonstrated by hybridization of the nuclear transcripts to subcloned spacer DNA. Although the bulk of the RNA transcripts are greater than 2000 bases long, the histone-specific transcripts are of discrete sizes ranging from 100 bases to about 1100 bases long. Each histone gene hybridizes with at least one of the larger transcripts and with a different subset of smaller RNAs. We do not detect any giant polycistronic transcript spanning the entire histone repeat unit.
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PMID:Sea urchin nuclei use RNA polymerase II to transcribe discrete histone RNAs larger than messengers. 69 39

The artificially stimulated decidual cell reaction has been used as a model to study changes occurring in the uterus at the time of implantation. Activities of RNA polymerases I, II and III were measured in uterine nuclei isolated from ovariectomized non-primed mice, hormonally primed mice, and hormonally primed mice following stimulation of the decidual cell reaction. Activities of all three RNA polymerases increased following hormonal priming of ovariectomized mice. In nuclei from stimulated uterine horns, activities of RNA polymerases I and III increased 9 h after stimulation of the decidual cell reaction and remained elevated through 21 h. RNA polymerase II activity did not change following stimulation of the decidual cell reaction. These changes in RNA polymerase activities occur at the time of increased histone modifications and may result from changes in the template capacity.
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PMID:Changes in RNA polymerase activity in isolated mouse uterine nuclei during the decidual cell reaction. 71 31

The effects of estrogen, progesterone and estrogen + progesterone combined on nuclear transcriptional processes in oviducts of immature chicks, previously withdrawn from estrogen, are reported. The responses to the steroids of the endogenous nuclear RNA polymerase activities, both nucleolar (I) and nucleoplasmic (II), the chromatin compositions and template capacities, and the appearance of ovalbumin messenger RNA (mRNA) are compared. When immature chicks (previously treated at 14 days with estrogen) are withdrawn from estrogen treatment, there is a gradual reduction in both polymerase activities. Diurnal variations in polymerase II activties in the oviduct of withdrawn chicks required that subsequent experiments include time-matched controls. The hormones alter RNA polymerase II and II activities in vivo as assayed in isolated nuclei. Progesterone represses the polymerase I and II activities, while estrogen alone and estrogen + progesterone enhance both polymerase activities immediately after injection. Diethylstillbestrol, a synthetic estrogen, causes changes similar to those of estrogen. The effects of these steroids on the polymerases are detected within 15 min of hormone injection. Changes in the capacities of chromatins to serve as template for RNA synthesis in general correlated with changes in polymerase II activities. Interestingly, in the case of estrogen treatment, the acidic chromatin protein (but not histone) levels fluctuate positively with the template capacities of the chromatin. An antagonism between estrogen and progesterone is observed in the responses of both RNA polymerases I and II activities as well as in the chromatin template capacity. Levels of messenger RNA coding for ovalbumin, as detected by hybridization with labeled complementary DNA, increase in oviducts of withdrawn chicks within 2--3 of the injection of estrogen, progesterone or estrogen + progesterone. This rapid accumulation of ovalbumin mRNA is not accompanied in each case by a similar increase in polymerase II activity or chromatin template capacity.
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PMID:Effects of estrogen and progesterone on transcription, chromatin and ovalbumin gene expression in the chick oviduct. 95 4

The initiation of RNA polymerase II transcription is controlled by DNA sequence-specific activator proteins, in combination with cofactor polypeptides whose function is poorly understood. Transcriptional cofactors of the CTF-1 activator were purified on the basis of their affinity for the regulatory protein. These purified cofactors were found to be required for CTF-1-regulated transcription, and they counteracted squelching by an excess of activator in in vitro reconstitution experiments. Interestingly, the cofactors possessed an inhibitory activity for basal transcription, which was relieved by the further addition of the activator. Histone H1 also contributes to the regulation of transcription by CTF-1, whereby the activator prevents repression of the basal transcription machinery by the histone. However, histone H1 could not replace the cofactors for CTF-1-regulated transcription, indicating that they possess distinct transcriptional properties. Furthermore, the purified cofactors were found to be required, together with the activator, in order to antagonize the histone-mediated repression of transcription. These results suggest that CTF-1 and its cofactors function by regulating the assembly of the basal transcription machinery onto the promoter when the latter is in competition with DNA-binding inhibitory proteins such as histone H1.
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PMID:Purified cofactors and histone H1 mediate transcriptional regulation by CTF/NF-I. 140 93

By using a DNase I footprinting assay, we have purified a factor by DNA affinity chromatography that binds to the minimal enhancer region of the Drosophila knirps gene and subsequently identified the protein as the core histone H2B. This inadvertent purification of a core histone as a putative sequence-specific DNA binding protein was due to a previously unknown property of H2B to interact with DNA in a periodic manner. Moreover, we found that each of the individual core histones, but not histone H1 or high mobility group protein 1, bound to the knirps enhancer to give a repetitive DNase I footprint pattern with a periodicity of about 10 base pairs, which is approximately one turn of the DNA helix. In addition, preparations containing the core histones H2A-H2B or H3-H4 yielded identical periodic DNase I footprint patterns on several different promoter and enhancer regions. These findings suggest that there are periodic, homotypic interactions between DNA-bound core histones that result from an alteration of the overall DNA structure such as the curvature rather than a specific sequence. We have also shown that histones H2A-H2B can repress initiation of transcription by RNA polymerase II. The phenomena described here may reflect histone-DNA interactions in non-nucleosomal stretches of chromatin and could be involved in some aspects of either rotational or translational positioning of nucleosomes. Furthermore, these findings indicate that a repeated 10 bp DNase I ladder, which has previously been considered to be a property of an intact nucleosome, can also be generated with subnucleosomal components. It will thus be necessary to reevaluate the criteria applied to the analysis of nucleosomes both in vivo and in vitro.
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PMID:Periodic binding of individual core histones to DNA: inadvertent purification of the core histone H2B as a putative enhancer-binding factor. 148 Apr 89

Under conditions unfavorable to growth, the nematode Caenorhabditis elegans enters a developmentally arrested stage, the dauer larva. We have examined gene expression in the dauer larva and during recovery from the dauer stage. Run-on transcription assays with isolated nuclei reveal a depression of general RNA polymerase II transcription to 11-17% of that in other stages. Transcription of individual gene families (including actin, collagen, hsp70, and histone) is similarly depressed relative to actively growing stages. Dauer larvae are, however, capable of being induced for heat shock messages, indicating that they are competent to initiate and elongate transcripts. For most genes surveyed, reduced transcription in dauer larvae correlates with a decrease in message abundance. Hsp70 mRNA, however, is transcribed at lower rates but accumulates at levels comparable to those in other stages. Interestingly, dauer larvae are 15-fold enriched in a mRNA for a C. elegans hsp90 gene. Hsp90 mRNA accumulation is regulated at least in part by differential stability. Dauer larvae thus appear to have a unique pattern of gene expression. Upon placement in food, dauer larvae reenter the developmental pathway as late-stage larvae. Dauer recovery is accompanied by a temporally regulated sequence of gene expression. At least four distinct patterns of gene expression can be distinguished during exit from the dauer stage. Steady-state levels of hsp70 and polyubiquitin mRNA rise sharply within 75 min of recovery before declining by the fourth hour. Actin and histone mRNAs increase steadily following 2-4 hr of recovery, whereas myosin mRNA increases after 10 hr. In contrast, hsp90 mRNA declines sharply within the first 75 min of recovery. Changes in mRNA populations during dauer formation and exit may be physiologically relevant.
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PMID:Gene expression in the Caenorhabditis elegans dauer larva: developmental regulation of Hsp90 and other genes. 157 99


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