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)

Rad26, the yeast homologue of human Cockayne syndrome group B protein, and Rpb9, a nonessential subunit of RNA polymerase II, have been shown to mediate two subpathways of transcription-coupled DNA repair in yeast. Here we show that Rad26- and Rpb9-mediated repair in the yeast GAL1 gene is differently modulated by different promoter elements. The initiation site and efficiency of Rad26-mediated repair in the transcribed strand are determined by the upstream activating sequence (UAS) but not by the TATA or local sequences. The role of UAS in determining the Rad26-mediated repair is not through loading of RNA polymerase II or the transcriptional regulatory complex SAGA. However, both the UAS and the TATA sequences are essential for confining Rad26-mediated repair to the transcribed strand. Mutation of the TATA sequence, which greatly reduces transcription, or deletion of the TATA or mutation of the UAS, which completely abolishes transcription, causes Rad26-mediated repair to occur in both strands. Rpb9-mediated repair only occurs in the transcribed strand and is efficient only in the presence of both TATA and UAS sequences. Also, the efficiency of Rpb9-mediated repair is dependent on the SAGA complex. Our results suggest that Rad26-mediated repair can be either transcription-coupled, provided that a substantial level of transcription is present, or transcription-independent, if the transcription is too low or absent. In contrast, Rpb9-mediated repair is strictly transcription-coupled and is efficient only when the transcription level is high.
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PMID:Modulation of Rad26- and Rpb9-mediated DNA repair by different promoter elements. 1702 24

Nucleotide excision repair (NER) is a conserved DNA repair mechanism capable of removing a variety of helix-distorting DNA lesions. A specialized NER pathway, called transcription coupled NER (TC-NER), refers to preferential repair in the transcribed strand of an actively transcribed gene. To be distinguished from TCR-NER, the genome-wide NER process is termed as global genomic NER (GG-NER). In Saccharomyces cerevisiae, GG-NER is dependent on Rad7, whereas TC-NER is mediated by Rad26, the homolog of the human Cockayne syndrome group B protein, and by Rpb9, a non-essential subunit of RNA polymerase II. Tfb5, the tenth subunit of the transcription/repair factor TFIIH, is implicated in one group of the human syndrome trichothiodystrophy. Here, we show that Tfb5 plays different roles in different NER pathways in yeast. No repair takes place in the non-transcribed strand of a gene in tfb5 cells, or in both strands of a gene in rad26 rpb9 tfb5 cells, indicating that Tfb5 is essential for GG-NER. However, residual repair occurs in the transcribed strand of a gene in tfb5 cells, suggesting that Tfb5 is important, but not absolutely required for TC-NER. Interestingly, substantial repair occurs in the transcribed strand of a gene in rad7 tfb5 and rad7 rpb9 tfb5 cells, indicating that, in the absence of GG-NER, Tfb5 is largely dispensable for Rad26 mediated TC-NER. Furthermore, we show that no repair takes place in the transcribed strand of a gene in rad7 rad26 tfb5 cells, suggesting that Tfb5 is required for Rpb9 mediated TC-NER. Taken together, our results indicate that Tfb5 is partially dispensable for Rad26 mediated TC-NER, especially in GG-NER deficient cells. However, this TFIIH subunit is required for other NER pathways.
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PMID:Tfb5 is partially dispensable for Rad26 mediated transcription coupled nucleotide excision repair in yeast. 1764 94

RNA polymerase II is unable to bypass bulky DNA lesions induced by agents like ultraviolet light (UV light) and cisplatin that are located in the template strand of active genes. Arrested polymerases form a stable ternary complex at the site of DNA damage that is thought to pose an impediment to the repair of these lesions. Transcription-coupled nucleotide excision repair (TC-NER) preferentially repairs these DNA lesions through an incompletely defined mechanism. Based on elegant in vitro experiments, it was hypothesized that the transcription elongation factor IIS (TFIIS) may be required to couple transcription to repair by catalyzing the reverse translocation of the arrested polymerase, allowing access of repair proteins to the site of DNA damage. However the role of TFIIS in this repair process has not been tested in vivo. Here, silencing TFIIS using an RNA interference strategy did not affect the ability of cells to recover nascent RNA synthesis following UV exposure or the ability of cells to repair a UV-damaged reporter gene while a similar strategy to decrease the expression Cockayne syndrome group B protein (CSB) resulted in the expected repair defect. Furthermore, RNA interference against TFIIS did not increase the sensitivity of cells to UV light or cisplatin while decreased expression of CSB did. Taken together, these results indicate that TFIIS is not limiting for the repair of transcription-blocking DNA lesions and thus the present work does not support a role for TFIIS in TC-NER.
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PMID:RNA interference against transcription elongation factor SII does not support its role in transcription-coupled nucleotide excision repair. 2107 Jul 92

Why mammalian cells possess multiple DNA glycosylases (DGs) with overlapping substrate ranges for repairing oxidatively damaged bases via the base excision repair (BER) pathway is a long-standing question. To determine the biological role of these DGs, null animal models have been generated. Here, we report the generation and characterization of mice lacking Neil2 (Nei-like 2). As in mice deficient in each of the other four oxidized base-specific DGs (OGG1, NTH1, NEIL1, and NEIL3), Neil2-null mice show no overt phenotype. However, middle-aged to old Neil2-null mice show the accumulation of oxidative genomic damage, mostly in the transcribed regions. Immuno-pulldown analysis from wild-type (WT) mouse tissue showed the association of NEIL2 with RNA polymerase II, along with Cockayne syndrome group B protein, TFIIH, and other BER proteins. Chromatin immunoprecipitation analysis from mouse tissue showed co-occupancy of NEIL2 and RNA polymerase II only on the transcribed genes, consistent with our earlier in vitro findings on NEIL2's role in transcription-coupled BER. This study provides the first in vivo evidence of genomic region-specific repair in mammals. Furthermore, telomere loss and genomic instability were observed at a higher frequency in embryonic fibroblasts from Neil2-null mice than from the WT. Moreover, Neil2-null mice are much more responsive to inflammatory agents than WT mice. Taken together, our results underscore the importance of NEIL2 in protecting mammals from the development of various pathologies that are linked to genomic instability and/or inflammation. NEIL2 is thus likely to play an important role in long term genomic maintenance, particularly in long-lived mammals such as humans.
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PMID:Neil2-null Mice Accumulate Oxidized DNA Bases in the Transcriptionally Active Sequences of the Genome and Are Susceptible to Innate Inflammation. 2624 4

DNA lesions block cellular processes such as transcription, inducing apoptosis, tissue failures, and premature aging. To counteract the deleterious effects of DNA damage, cells are equipped with various DNA repair pathways. Transcription-coupled repair specifically removes helix-distorting DNA adducts in a coordinated multistep process. This process has been extensively studied; however, once the repair reaction is accomplished, little is known about how transcription restarts. In this study, we show that, after UV irradiation, the cyclin-dependent kinase 9 (CDK9)/cyclin T1 kinase unit is specifically released from the HEXIM1 complex and that this released fraction is degraded in the absence of the Cockayne syndrome group B protein (CSB). We determine that UV irradiation induces a specific Ser2 phosphorylation of the RNA polymerase II and that this phosphorylation is CSB dependent. Surprisingly, CDK9 is not responsible for this phosphorylation but instead might play a nonenzymatic role in transcription restart after DNA repair.
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PMID:CSB-Dependent Cyclin-Dependent Kinase 9 Degradation and RNA Polymerase II Phosphorylation during Transcription-Coupled Repair. 3060 96