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Systematic mutagenesis identifies p52/Tfb2 residues required for XPB/Ssl2 function within TFIIH and genetic interactions with TFB6

ABSTRACT: TFIIH is an evolutionarily conserved complex that plays central roles in both RNA polymerase II (pol II) transcription and DNA repair. As an integral component of the pol II Pre-Initiation Complex, TFIIH regulates the activity of the pol II enzyme in numerous ways. One of the essential functions of TFIIH resides in its XPB/Ssl2 subunit. XPB/Ssl2 is an ATP-dependent DNA translocase that stimulates promoter opening prior to transcription initiation. Crosslinking-mass spectrometry and cryo-EM results have shown a conserved interaction network involving XPB/Ssl2 and the C-terminal Hub region of the p52/Tfb2 core subunit. Here, we systematically mutagenized the HubA region of Tfb2 and screened for growth phenotypes in a TFB6 deletion background in Saccharomyces cerevisiae. We identified six lethal and twelve conditional mutants. Growth phenotypes of all but three of the conditional mutants were suppressed in the presence of Tfb6, thus identifying a functional interaction between Tfb2 HubA mutants and Tfb6, a protein that dissociates Ssl2 from TFIIH. Biochemical analysis of p52/Tfb2 mutants with severe growth phenotypes revealed defects in XPB/Ssl2 association. Further characterization of these Tfb2 mutant cells revealed defects in induction of Gal genes, and reduced occupancy TFIIH and pol II at Gal gene promoters, suggesting that functional TFIIH is required for proper Pol II recruitment to PICs in vivo. Consistent with recent structural models of TFIIH, our results identify key residues in the p52/Tfb2 HubA domain that are required for stable incorporation of XPB/Ssl2 into TFIIH, and for pol II transcription.

ORGANISM(S): Saccharomyces cerevisiae

PROVIDER: GSE196069 | GEO | 2022/06/30

REPOSITORIES: GEO

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Systematic mutagenesis identifies p52/Tfb2 residues required for XPB/Ssl2 function within TFIIH and genetic interactions with TFB6

Project description:TFIIH is an evolutionarily conserved complex that plays central roles in both RNA polymerase II (pol II) transcription and DNA repair. As an integral component of the pol II Pre-Initiation Complex (PIC), TFIIH regulates the activity of the pol II enzyme in numerous ways. The TFIIH subunit XPB/Ssl2 is an ATP-dependent DNA translocase that stimulates promoter opening prior to transcription initiation. Crosslinking-mass spectrometry and cryo-EM results have shown a conserved interaction network involving XPB/Ssl2 and the C-terminal Hub region of the TFIIH p52/Tfb2 subunit. Here, we systematically mutagenized the HubA region of Tfb2 and screened for growth phenotypes in a TFB6 deletion background in Saccharomyces cerevisiae. We identified six lethal and twelve conditional mutants. Slow growth phenotypes of all but three conditional mutants were relieved in the presence of TFB6, thus identifying a functional interaction between Tfb2 HubA mutants and Tfb6, a protein that dissociates Ssl2 from TFIIH. Biochemical analysis of Tfb2 mutants with severe growth phenotypes revealed defects in Ssl2 association, with similar results in human cells. Further characterization of these tfb2 mutant cells revealed defects in GAL gene induction, and reduced occupancy of TFIIH and pol II at GAL gene promoters, suggesting that functionally competent TFIIH is required for proper pol II recruitment to PICs in vivo. Consistent with recent structural models of TFIIH, our results identify key residues in the p52/Tfb2 HubA domain that are required for stable incorporation of XPB/Ssl2 into TFIIH, and for pol II transcription.

2023-03-11 | PXD035576 | Pride

Systematic mutagenesis of TFIIH subunit p52/Tfb2 identifies residues required for XPB/Ssl2 subunit function and genetic interactions with TFB6

Project description:TFIIH is an evolutionarily conserved complex that plays central roles in both RNA polymerase II (pol II) transcription and DNA repair. As an integral component of the pol II Pre-Initiation Complex (PIC), TFIIH regulates pol II enzyme activity in numerous ways. The TFIIH subunit XPB/Ssl2 is an ATP-dependent DNA translocase that stimulates promoter opening prior to transcription initiation. Crosslinking-mass spectrometry and cryo-EM results have shown a conserved interaction network involving XPB/Ssl2 and the C-terminal Hub region of the TFIIH p52/Tfb2 subunit, but the functional significance of specific residues is unclear. Here, we systematically mutagenized the HubA region of Tfb2 and screened for growth phenotypes in a TFB6 deletion background in Saccharomyces cerevisiae. We identified six lethal and twelve conditional mutants. Slow growth phenotypes of all but three conditional mutants were relieved in the presence of TFB6, thus identifying a functional interaction between Tfb2 HubA mutants and Tfb6, a protein that dissociates Ssl2 from TFIIH. Our biochemical analysis of Tfb2 mutants with severe growth phenotypes revealed defects in Ssl2 association, with similar results in human cells. Further characterization of these tfb2 mutant cells revealed defects in GAL gene induction, and reduced occupancy of TFIIH and pol II at GAL gene promoters, suggesting that functionally competent TFIIH is required for proper pol II recruitment to PICs in vivo. Consistent with recent structural models of TFIIH, our results identify key residues in the p52/Tfb2 HubA domain that are required for stable incorporation of XPB/Ssl2 into TFIIH, and for pol II transcription.

2022-09-07 | PXD036107 | Pride

Ssl2/TFIIH Function in Transcription Start Site Scanning by RNA Polymerase II in Saccharomyces cerevisiae

Project description:The initial step of RNA polymerase II (Pol II) transcription involves a large number of transcription factors and arises at multiple sites within most promoters. TFIIH is an essential, multi-subunit transcription factor that assembles on promoter DNA with Pol II and five other general transcription factors (GTFs) to form a pre-initiation complex (PIC) for basal transcription. During transcription initiation, TFIIH melts promoter DNA through the ATPase activity of its Ssl2 subunit. In the model eukaryote Saccharomyces cerevisiae, after DNA melting, Pol II scans downstream for usable transcription start sites (TSSs). To understand the function of Ssl2/TFIIH in promoter scanning and TSS selection, we identified novel alleles of SSL2 in genetic screens for mutants defective in TSS distribution that may potentially arise from altered scanning. Consistent with this notion, these ssl2 alleles alter scanning in ways that are distinct from how changes to the Pol II active site alter scanning and this difference is observed genome-wide. Our investigations support two major pathways in controlling promoter scanning and TSS selection, one controlling the efficiency of initiation through Pol II activity or factors regulating Pol II activity; another network appears to control the processivity of scanning by Ssl2/TFIIH.

2021-08-28 | GSE182792 | GEO

Systematic mutagenesis identifies p52/Tfb2 residues required for XPB/Ssl2 function within TFIIH and genetic interactions with TFB6

Project description:Systematic mutagenesis identifies p52/Tfb2 residues required for XPB/Ssl2 function within TFIIH and genetic interactions with TFB6

| PRJNA803201 | ENA

Stably-paused genes revealed through inhibition of transcription initiation by the TFIIH inhibitor Triptolide

Project description:Transcription by RNA Polymerase II (Pol II) in metazoan is regulated in several steps, including preinitiation complex (PIC) formation, initiation, Pol II escape, productive elongation, cotranscriptional RNA-processing and termination. Genome-wide studies have demonstrated that the phenomenon of promoter-bound Pol II pausing is widespread, especially for genes involved in developmental and stimulus-responsive pathways. However, a mechanistic understanding of the paused Pol II states at promoters is limited. For example, at a global level, it’s unclear to what extent the engaged paused Pol II is stably tethered to the promoter or undergoes rapid cycles of initiation and termination. Here we used the small molecule Triptolide (TPL), an XPB/TFIIH inhibitor, to block transcriptional initiation followed by measuring Pol II occupancy by ChIP-seq. This inhibition of initiation enables us to investigate different states of paused Pol II. Specifically, our global analysis reveals that most genes with paused Pol II, as defined by pausing index, show significant clearance of Pol II during the period of TPL treatment. Our study further identifies a group of genes with unexpectedly stably-paused Pol II, with unchanged Pol II occupancy even after one hour of inhibition of initiation. This group of genes constitutes a small portion of all paused genes defined by the conventional criterion of pausing index. These findings could pave the way for evaluating the contribution of different elongation/pausing factors on different states of Pol II pausing in developmental and other stimulus-responsive pathways. ChIP-Seq of total/Ser5P Pol II in HCT116 cells treated with DMSO or TPL in serum starvation/activation or normal conditions. Nascent RNA-seq in HCT116 cells treated with DMSO or TPL in starved condition.

2015-01-05 | E-GEOD-63314 | biostudies-arrayexpress

Stably-paused genes revealed through inhibition of transcription initiation by the TFIIH inhibitor Triptolide

2015-01-05 | GSE63314 | GEO

Structure of transcription preinitiation complex engaged with the +1 nucleosome

Project description:The preinitiation complex (PIC) assembles on promoters of protein-coding genes to position RNA polymerase II (Pol II) for transcription initiation. Previous structural studies revealed the PIC on different promoters, but did not address how the PIC assembles in chromatin. In the yeast Saccharomyces cerevisiae, PIC assembly occurs adjacent to the +1 nucleosome that is positioned downstream of the core promoter. Here we present the cryo-EM structure of the yeast PIC bound to promoter DNA and the +1 nucleosome at a resolution of 3.4–3.9 Å. The general transcription factor TFIIH forms four contacts with the nucleosome, indicating how PIC assembly can be assisted by the +1 nucleosome. The TFIIH subunit Ssl2 (XPB in human TFIIH) forms a wedge between promoter DNA and the nucleosome, stabilizing two turns of DNA that are detached from the nucleosome. During subsequent scanning for the transcription start site (TSS), three additional turns of DNA can be detached before the partially unraveled nucleosome may counteract further scanning, explaining why TSSs are located at a distance of ~60 bp from the dyad of the +1 nucleosome in yeast.

2023-03-11 | PXD029840 | Pride

Genome binding profile of TFIIH helicases XPB and XPD in HT1080 cells

Project description:The conserved TFIIH helicases XPB and XPD play key roles in transcription initiation and DNA repair. To investigate the functions of these helicases on a genome-wide scale, we performed ChIP-seq of endogenous XPB and XPD in the HT1080 human fibrosarcoma cell line.

2014-02-18 | GSE44849 | GEO

Genome binding profile of TFIIH helicases XPB and XPD in HT1080 cells

2014-02-18 | E-GEOD-44849 | biostudies-arrayexpress

Structure of TFIIK for phosphorylation of CTD of RNA polymerase II

Project description:TFIIH is a 10-protein complex that is conserved through out eukaryotes. TFIIH has two primary cellular functions: transcription initiation and nucleotide excision repair (NER). In transcription initiation, TFIIH acts as a structural scaffold, phosphorylates the RNA polymerase II (pol II) C-terminal domain (CTD) and translocates promoter DNA through the pol II active site to facilitate start site selection. In NER, again is a structural scaffold, opens a bubble around damaged DNA and scans the damaged strand for bulky lesions. In yeast (Saccharomyces cerevisiae), TFIIH is composed of the two helicases Ssl2 and Rad3, the scaffolding subunits Tfb1, Tfb2, Tfb4 and Ssl1 and the kinase subunits Kin28, Ccl1 and Tfb3.

2021-07-07 | PXD021211 | Pride

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