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)

The transcription factor TFIIH continues to be a subject of interest. In addition to its function as a repair and transcription factor, TFIIH includes a cyclin-dependent kinase and a cyclin, which raises the possibility that nucleotide excision repair (NER), RNA polymerase II transcription and cell cycle control are connected. Progress in mechanistic studies of NER include the identification of dual incision activities operating on either side of base damage and the isolation of a repairosome supercomplex in yeast. Additionally, NER has been demonstrated in reconstituted human and yeast systems, both of which include TFIIH.
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PMID:DNA repair and transcription. 872 69

The Kin28 protein kinase interacts physically and genetically with cyclin Ccl1. Kin28 has been reported recently to be involved in the in vivo phosphorylation of the largest subunit of RNA polymerase II (Rpb1) in Saccharomyces cerevisiae. Now, we show that in a strain harboring a conditional ccl1-ts mutation, the C-terminal domain (CTD) of the Rpb1 subunit is under-phosphorylated at restrictive temperature. The transcription of a set of genes, chosen at random, is severely affected in a kin28-ts mutant shifted at restrictive temperature. Here, we report that the same set of genes requires a functional CCL1 gene product to be transcribed. These findings, added to previously published data, establishes that Kin28p is a cyclin-dependent kinase (CDK) with Ccl1p as a companion, both of them being necessary for general transcription and CTD phosphorylation.
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PMID:Ccl1, a cyclin associated with protein kinase Kin28, controls the phosphorylation of RNA polymerase II largest subunit and mRNA transcription. 876 64

Previously, we showed that the viral transactivator proteins E1A and VP16 specifically interact with a cellular CTD kinase activity in vitro. We now report that E1A and VP16 complexes contain human CDK8, a newly identified member of the cyclin-dependent kinase family that has been shown to be a component of the RNA polymerase II (RNAP II) holoenzyme complex. The presence of CDK8 in the E1A- and VP16-containing complexes is specific for a functional activation domain of these viral transactivators, strongly suggesting that this association is relevant for the transactivation function of E1A and VP16. We show that CDK8 is associated with CTD kinase activity and that CDK8 co-fractionates with E1A- and VP16-associated CTD kinase activity over several chromatography columns. Therefore, CDK8 is likely responsible for the E1A- and VP16-associated CTD kinase activity. Gel filtration chromatography indicates that the E1A- and VP16-associated CTD kinase activity has a molecular size of approximately 1.5 MDa and contains cyclin C and the human homolog of SRB7 in addition to CDK8. This implies that E1A and VP16 associate with the RNAP II holoenyzme. We also looked at the transcriptional activity of CDK8 and found that CDK8 can function as a transcriptional activator when fused to the DNA binding domain of GAL4. Surprisingly, the ability of GAL4-CDK8 to activate transcription in this assay was not dependent on the kinase activity of CDK8, since a kinase-deficient mutant of CDK8 stimulated transcription nearly as well as wild-type GAL4-CDK8. This suggests that CDK8 may play a role in transcription that is distinct from its ability to function as a CTD kinase.
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PMID:Viral transactivators E1A and VP16 interact with a large complex that is associated with CTD kinase activity and contains CDK8. 887 57

p21(WAF1/CIP1) is a universal cyclin-dependent kinase (cdk) inhibitor, the expression of which is regulated by p53-dependent and p53-independent pathways. We examined p21(WAF1/CIP1) expression in and p53 status of 21 primary hepatocellular carcinomas (HCCs) by reverse-transcriptase polymerase chain reaction (RT-PCR) and by PCR single-strand conformation polymorphism (PCR-SSCP) analysis. p21(WAF1/CIP1) messenger RNA expression was reduced markedly in 8 of 21 HCCs (38.1%) and 5 of these 8 HCCs bore p53 mutations. The relative p21(WAF1/CIP1) messenger RNA expression value of HCCs with p53 mutations (.73 +/- .13 U, n = 6) was significantly lower than that of HCCs with wild-type p53 (1.00 +/- 0.21 U, n = 14; P < .01). The p21(WAF1/CIP1) expression levels in cancerous tissues (.73 +/- .13 U) were significantly reduced in comparison with those in noncancerous tissues (.97 +/- .13 U) (P < .01) in the 6 cases with p53 mutations. These data indicate that p21(WAF1/CIP1) expression in HCCs is predominantly regulated by dependence on p53 and that reduced p21(WAF1/CIP1 expression may participate in hepatocarcinogenesis.
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PMID:Reduced p21(WAF1/CIP1) expression and p53 mutation in hepatocellular carcinomas. 904 1

The human cyclin H, a protein normally associated with the cyclin-dependent kinase cdk7, was overexpressed in Escherichia coli using a T7 RNA polymerase expression system and further purified to apparent homogeneity. The purified recombinant cyclin H is similar to the endogenous one according to the following criteria: molecular weight, microsequencing and mass spectra studies, ability to interact with cdk7, and regulatory kinase activity. The scale-up of cyclin H purification is described.
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PMID:Expression in Escherichia coli: purification and characterization of cyclin H, a subunit of the human general transcription/DNA repair factor TFIIH. 905 80

The Tax protein of human T-cell leukemia virus type 1 (HTLV-1) is a potent activator of viral transcription. Tax also activates the expression of specific cellular genes involved in the control of T-lymphocyte growth via effects on cellular transcription factors, including members of the NF-kappaB/cRel family. Immunocytochemistry and electron microscopy were used to characterize the intracellular localization of Tax and identify cellular factors which are the potential targets for its transcriptional activity. These studies indicated that Tax localizes in discrete nuclear foci in T lymphocytes transformed by HTLV-1 and in cells transduced with Tax expression vectors. The Tax-containing foci are complex nuclear structures comprising a central core in which Tax colocalizes with splicing factor Sm. In addition to splicing factors Sm and SC-35, the Tax-containing nuclear structures also contain transcriptional components, including the largest subunit of RNA polymerase II and cyclin-dependent kinase CDK8. The inclusion of the two subunits of NF-kappaB, p50 and RelA, and the presence of the mRNA from a gene specifically activated by Tax through NF-kappaB binding sites suggest that these unique nuclear structures participate in Tax-mediated activation of gene expression via the NF-kappaB pathway.
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PMID:The human T-cell leukemia virus type 1 transactivator protein Tax colocalizes in unique nuclear structures with NF-kappaB proteins. 909 20

The cyclin-dependent kinase (CDK)-activating kinase CAK has been proposed to function in the control of cell cycle progression, DNA repair and RNA polymerase II (pol II) transcription. Most CAK exists as complexes of three subunits: CDK7, cyclin H (CycH) and MAT1. This tripartite CAK occurs in a free form and in association with 'core' TFIIH, which functions in both pol II transcription and DNA repair. We investigated the substrate specificities of different forms of CAK. Addition of the MAT1 subunit to recombinant bipartite CDK7-CycH switched its substrate preference to favour the pol II large subunit C-terminal domain (CTD) over CDK2. We suggest that the MAT1 protein, previously shown to function as an assembly factor for CDK7-CycH, also acts to modulate CAK substrate specificity. The substrate specificities of natural TFIIH and free CAK were also compared. TFIIH had a strong preference for the CTD over CDK2 relative to free CAK. TFIIH, but not free CAK, could efficiently hyperphosphorylate the CTD. In the context of TFIIH, the kinase also acquired specificity for the general transcription factors TFIIE and TFIIF which were not recognized by free CAK. We conclude that the substrate preference of the CDK7-CycH kinase is governed by association with both MAT1 and 'core' TFIIH.
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PMID:Regulation of CDK7 substrate specificity by MAT1 and TFIIH. 913 Jul 9

Genes for the Tfb2, Tfb3, and Tfb4 subunits of yeast RNA polymerase transcription factor IIH (TFIIH) are described. All three genes are essential for cell viability, and antibodies against Tfb3 specifically inhibit transcription in vitro. A C-terminal deletion of Tfb2 caused a defect in nucleotide excision repair, as shown by UV sensitivity of the mutant strain and loss of nucleotide excision repair activity in cell extracts (restored by the addition of purified TFIIH). An interaction between Tfb3 and the Kin28 subunit of TFIIH was detected by the two-hybrid approach, consistent with a role for Tfb3 in linking kinase and core domains of the factor. The deduced amino acid sequence of Tfb2 is similar to that of the 52-kDa subunit of human TFIIH, while Tfb3 is identified as a RING finger protein homologous to the 36-kDa subunit of murine CAK (cyclin-dependent kinase activating kinase) and to the 32-kDa subunit of human TFIIH. Tfb4 is homologous to p34 of human TFIIH and is identified as the weakly associated 37-kDa subunit of the yeast factor. These and other findings reveal a one-to-one correspondence and high degree of sequence similarity between the entire set of yeast and human TFIIH polypeptides.
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PMID:Genes for Tfb2, Tfb3, and Tfb4 subunits of yeast transcription/repair factor IIH. Homology to human cyclin-dependent kinase activating kinase and IIH subunits. 923 28

Kin28/Cell, a cyclin-dependent kinase, is essential for the in vivo phosphorylation of the C-terminal domain of the largest subunit of RNA polymerase II in Saccharomyces cerevisiae. In a search for mutations co-lethal with a thermosensitive kin28 mutation, we have identified genes whose products interact functionally with Kin28. In the present work, we have studied a new complementation group of synthetic lethal mutations. The corresponding gene, RIG2, encodes a predicted RING finger protein. Rig2 is likely to be a homolog of MAT1 of higher eukaryotes which forms a ternary complex with MO15(cdk7) and cyclin H. Our genetic data suggest that Rig2 is a component of transcription factor TFIIH. Transcription activity in a rig2-ts mutant is impeded at restrictive temperature. However, none of the rig2-ts mutants obtained was UV sensitive, suggesting that Rig2 is dispensable for nucleotide excision repair.
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PMID:Rig2, a RING finger protein that interacts with the Kin28/Ccl1 CTD kinase in yeast. 929 30

Affinity chromatography on columns containing the immobilized monomeric transcriptional elongation factor TFIIS or the essential large subunit, Elongin A, of the trimeric elongation factor, Elongin, was used to purify a human RNA polymerase II holoenzyme from HeLa whole cell extract. This holoenzyme contained nearstoichiometric amounts of all the general transcription factors, TFIIB, TFIID (TBP + TAFIIs), TFIIE, TFIIF, and TFIIH, required to accurately initiate transcription in vitro at the adenovirus major late promoter. It behaved as a large complex, slightly smaller than 70 S ribosomes, during gel filtration chromatography, and contained nearly half the TFIID that was present in the extract used for the affinity chromatography. It also contained the cyclin-dependent kinase CDK8, a human homologue of the Saccharomyces cerevisiae holoenzyme subunit SRB10, and many other polypeptides. Efficient interaction of holoenzyme with TFIIS or Elongin A required only the amino-terminal region of either protein. These regions are similar in amino acid sequence but dispensable for TFIIS or Elongin to regulate elongation in vitro by highly purified RNA polymerase II. The transcriptional activators GAL4-VP16 and GAL4-Sp1 activated transcription in vitro by purified holoenzyme in the absence of any additional factors.
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PMID:Interaction of elongation factors TFIIS and elongin A with a human RNA polymerase II holoenzyme capable of promoter-specific initiation and responsive to transcriptional activators. 930 22


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