General transcription and DNA repair factor IIH helicase/translocase subunit XPB/SSL2

UniProtKB accession:  Q00578

Grouped By:  Matching UniProtKB accession

UniProtKB description:  ATP-dependent DNA translocase (PubMed:25775526). Component of the general transcription and DNA repair factor IIH (TFIIH) core complex. When complexed to CDK-activating kinase (CAK), involved in RNA transcription by RNA polymerase II (PubMed:14500720, PubMed:7693549, PubMed:7813015, PubMed:7961739, PubMed:8202161, PubMed:8269516, PubMed:8631896). May have 3'-5' helicase activity alone, the TFIIH core however has no 3'-5' helicase activity (PubMed:25775526). Also involved in transcription-coupled nucleotide excision repair (NER) of damaged DNA (PubMed:7693549, PubMed:7813015, PubMed:8202161, PubMed:8269516, PubMed:8631896). In NER, TFIIH acts by opening DNA around the lesion to allow the excision of the damaged oligonucleotide and its replacement by a new DNA fragment. The ATPase activity of XPB/SSL2, but not its helicase activity, is required for DNA opening. In transcription, TFIIH has an essential role in transcription initiation. When the pre-initiation complex (PIC) has been established, TFIIH is required for promoter opening and promoter escape. The ATP-dependent helicase activity of XPB/SSL2 is required for promoter opening and promoter escape. XPB/SSL2 acts as a double-stranded DNA translocase, promoting DNA opening by tracking in a 5'-3' dirction along the nontemplate promoter strand, rotating and inserting DNA into the Pol II active site cleft, leading to DNA unwinding (PubMed:25775526). A dsDNA-stimulated ATPase, dATP and ATP are equally good substrates (PubMed:25775526). May also use this translocase mechanism during DNA repair rather than physically wedging open damaged DNA (PubMed:25775526).