Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.7.6 (RNA polymerase)
 34,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A special class of non-histone protein ("tight protein") is identified in purified HeLa cell chromatin on the basis of its failure to dissociate from the DNA at very high ionic strength (2.5 M NaCl-5.0 M urea), where over 92% of the total chromatin protein is released. The tight proteins are insoluble in 0.4 N H2SO4 and lack histones as determined by polyacrylamide gel electrophoresis. They have molecular weights between 14,000 and 85,000 with over 70% of the polypeptide chains between 14,000 and 30,000 mol wt. This is the same size range as the non-histone proteins which others have found to display species-specific DNA binding in vitro. There is approximately one molecule of tight protein per 275 DNA base pairs. The tight proteins are characterized by much higher rates of labeling with amino acids than the histones and non-histone chromatin proteins that are dissociated from the DNA by high ionic strength, but they have the lowest phosphorylation levels. Chromatin fractionation experiments were performed to investigate the distribution of tight proteins between template-active and template-inactive regions. Under specific conditions, spleen DNase (DNase II) selectively shears those portions of HeLa cell chromatin that contain nascent RNA transcripts. This nascent RNA-enriched chromatin fraction also contains a high level of the proteins known to be complexed with heterogeneous nuclear RNA in ribonucleoprotein particles and contains over 70% of the RNA polymerase activity of total chromatin. When this method was employed to investigate the distribution of tight proteins, they were found to be almost entirely confined to the template-inactive fraction. Although these experiments do not elucidate the precise function of these proteins, they identify, for the first time, a particular subclass of non-histone chromosomal protein which is distributed asymmetrically between transcriptionally active and inactive chromatin regions.
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PMID:A special class of non-histone protein tightly complexed with template-inactive DNA in chromatin. 114 2

A non-histone chromosomal protein of Mr = 75,000 was isolated from Drosophila embryos. The distribution pattern of this protein was determined by indirect immunofluorescence on salivary gland chromosomes of Drosophila melanogaster third instar larvae and compared with the distribution pattern of RNA polymerase II. Despite its preferential association with transcriptionally active regions of the chromosomes there was in many cases an almost inverse correlation with the RNA polymerase II content of a given locus. We postulate a function of the Mr = 75,000 protein in posttranscriptional regulation of gene expression by storing the newly synthesized RNA.
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PMID:Isolation and distribution of a Drosophila protein preferentially associated with active regions of the genome. 249 46

The distribution patterns of chromosomal proteins from Drosophila can be observed by immunofluorescent staining of the polytene chromosomes from larval salivary glands. We have purified a non-histone chromosomal protein of Mr = 69,000 molecular weight which has a high affinity for DNA with little sequence specificity. Immunofluorescent staining indicates that this protein is preferentially associated with the inactive portions of the genome, including the centric heterochromatin and the condensed bands within the euchromatic arms of the chromosomes. Observation of both the heat shock loci 87A and 87C and the developmentally regulated loci 74EF and 75B shows an inverse correlation between immunofluorescent staining for the Mr = 69,000 protein and for RNA polymerase. The presence of this protein appears to be correlated with the packaging of the chromatin in an inactive form.
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PMID:Isolation and distribution of a Drosophila protein preferentially associated with inactive regions of the genome. 312 20

A non-histone chromosomal proteins was extracted from rat liver chromatin with 0.35 M NaCl and purified more than 2758 times to near homogeneity by hydroxyapatite, gel filtration, and phosphocellulose chromatography. The final fraction was greater than 95% pure as judged by non-denaturing gel electrophoresis. The protein, designated loosely bound non-histone chromosomal protein 1, had an observed molecular weight of 15 700. This protein was demonstrated to increase the amount of RNA synthesized in a heterologous (Escherichia coli RNA polymerase) transcription system and, therefore, this activity was also used to monitor its purification. The availability of highly purified loosely bound non-histone chromosomal protein 1 will make possible an examination of its structural and/or functional role in chromatin.
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PMID:Purification of a low molecular weight non-histone chromosomal protein. 735 13

A non-histone chromosomal protein was extracted and purified 177-fold from rat liver nuclei which stimulated RNA synthesis in vitro catalyzed by wheat germ RNA polymerase II with either liver chromatin, or native or denaturated calf thymus DNA as template. The stimulatory non-histone chromosomal protein fraction was characterized as having a molecular weight of 66 000 and a pI = 8.2--9.0. No activity was found with Escherichia coli RNA polymerase and liver chromatin. The binding of the stimulatory non-histone chromosomal protein occurred exclusively with the chromatin template and not with RNA polymerase II as assessed by its interference with actinomycin D but not with alpha-amanitin, respectively.
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PMID:Characterization of a non-histone chromosomal protein which stimulates RNA polymerase II. 737 Feb 64

The high-mobility group protein 14 (HMG-14) is a non-histone chromosomal protein that is preferentially associated with transcriptionally active chromatin. To assess the effect of HMG-14 on transcription by RNA polymerase II, in vivo-assembled chromatin with elevated amounts of HMG-14 was obtained. Here it is shown that HMG-14 enhanced transcription on chromatin templates but not on DNA templates. This protein stimulated the rate of elongation by RNA polymerase II but not the level of initiation of transcription. These findings suggest that the association of HMG-14 with nucleosomes is part of the cellular process involved in the generation of transcriptionally active chromatin.
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PMID:Stimulation of RNA polymerase II elongation by chromosomal protein HMG-14. 804 85

Ligand-dependent transcriptional regulation by nuclear receptors is believed to be mediated by intermediary factors (TIFs) acting on remodelling of the chromatin structure and/or the activity of the transcriptional machinery. The putative transcriptional mediator TIF1alpha is a nuclear protein kinase that has been identified via its interaction with liganded nuclear receptors, including retinoic acid (RAR), retinoid X (RXR) and estrogen (ER) receptors. Here, we demonstrate that TIF1alpha is a non-histone chromosomal protein tightly associated with highly accessible euchromatic regions of the genome. Immunofluorescence confocal microscopy reveals that TIF1alpha exhibits a finely granular distribution in euchromatin of interphase nuclei, while it is mostly excluded from condensed chromatin and metaphase chromosomes. Immunoelectron microscopy shows that, in contrast to the heterochromatin protein HP1alpha, most of TIF1alpha is associated with euchromatin, where it is preferentially localised on regions known to be sites for RNA polymerase II (perichromatin fibrils and borders between euchromatin and heterochromatin). Early mouse embryos as well as embryonal carcinoma (EC) and embryonic stem (ES) cells express high levels of TIF1alpha. These levels dramatically decrease during organogenesis and upon differentiation of P19 EC cells, indicating that TIF1alpha is preferentially expressed in undifferentiated pluripotent cells in the course of development. Therefore, TIF1alpha could belong to a novel class of chromatin-associated TIFs that facilitate the access of transregulators (e.g. liganded nuclear receptors) to their cognate sites in target genes, thereby participitating in the epigenetic control of transcription during embryonic development and cell differentiation.
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PMID:The putative nuclear receptor mediator TIF1alpha is tightly associated with euchromatin. 1031 60

An acidic non-histone chromosomal protein of low mobility group (LMG) with pI of 5-5.5 and molecular weight of 160 kDa (named LMG160), has been isolated from rat liver nuclei and its inhibitory effect on transcription of DNA in vitro has been detected in a heterologous prokaryotic in vitro transcription system (T7 RNA polymerase) and also confirmed in the homologous cell-free system of rat liver nuclear extract. The results indicate that in the presence of non-histone protein LMG160, in vitro RNA synthesis represses in the both systems, which can suggest a functional role for this non-histone chromosomal protein.
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PMID:Transcriptional inhibition by a non-histone protein from low mobility group in homologous and heterologous in vitro systems. 1738 33

Nhp6p is an architectural Saccharomyces cerevisiae non-histone chromosomal protein that bends DNA and plays an important role in transcription and genome stability. We used the split-ubiquitin system to isolate proteins that interact with Nhp6p in vivo, and we confirmed 11 of these protein-protein interactions with glutathione S-transferase pull-down experiments in vitro. Most of the Nhp6p-interacting proteins are involved in transcription and DNA repair. We utilized the ZDS1, PUR5 and UME6 genes, which are repressed by Nhp6p and its interacting partners Rpb4p and Med3p, to study the chromosomal localization of these three proteins in wild-type and gene deletion strains. Nhp6p, Med3p and Rpb4p were found at the promoters of ZDS1, PUR5 and UME6, indicating that the repressing effects the three proteins had on the expression of these three genes had been direct ones. We also found that Med3p inhibited promoter clearance of RNA polymerase II, which contained the dissociable subunit Rpb4p, while Nhp6p recruited Rpb4p to the basal promoters of ZDS1, PUR5 and UME6. Our results further suggest that Rpb4p inhibits transcription initiation but stimulates transcription elongation and that Nhp6p and Med3p regulate gene expression by controlling the local subunit composition of RNA polymerase II.
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PMID:Nhp6p and Med3p regulate gene expression by controlling the local subunit composition of RNA polymerase II. 1844 20