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FUNCTION ATP-dependent 5'-3' DNA helicase (PubMed:31253769, PubMed:8413672, PubMed:9771713). Component of the general transcription and DNA repair factor IIH (TFIIH) core complex, not absolutely essential for minimal transcription in vitro (PubMed:10024882, PubMed:17466626, PubMed:9771713). Required for transcription-coupled nucleotide excision repair (NER) of damaged DNA; recognizes damaged bases (PubMed:17466626, PubMed:23352696, PubMed:9771713). Sequestered in chromatin on UV-damaged DNA (PubMed:23352696). When complexed to CDK-activating kinase (CAK), involved in transcription by RNA polymerase II. 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 ATP-dependent helicase activity of XPD/ERCC2 is required for DNA opening. Involved in DNA lesion verification (PubMed:31253769). 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. Phosphorylation of the C-terminal tail (CTD) of the largest subunit of RNA polymerase II by the kinase module CAK controls the initiation of transcription. XPD/ERCC2 acts by forming a bridge between CAK and the core-TFIIH complex. The structure of the TFIIH transcription complex differs from the NER-TFIIH complex; large movements by XPD/ERCC2 and XPB/ERCC3 are stabilized by XPA which allow this subunit to contact ssDNA (PubMed:31253769, PubMed:33902107). Involved in the regulation of vitamin-D receptor activity. As part of the mitotic spindle-associated MMXD complex it plays a role in chromosome segregation. Might have a role in aging process and could play a causative role in the generation of skin cancers.CATALYTIC ACTIVITY Couples ATP hydrolysis with the unwinding of duplex DNA at the replication fork by translocating in the 5'-3' direction.CATALYTIC ACTIVITY ATP + H2O = ADP + phosphate + H(+)COFACTOR Binds 1 [4Fe-4S] cluster.ACTIVITY REGULATION Interaction with GTF2H2 (p44) results in stimulation of the 5'-3' helicase activity of this subunit (PubMed:9771713). DNA unwinding by this subunit in TFIIH is stimulated 4-fold by XPA and 20-fold by ERCC5/XPG (PubMed:31253769).BIOPHYSICOCHEMICAL PROPERTIES Optimum pH is 6.5 for both helicase and DNA-stimulated ATPase activity.SUBUNIT Component of the 7-subunit TFIIH core complex composed of XPB/ERCC3, XPD/ERCC2, GTF2H1, GTF2H2, GTF2H3, GTF2H4 and GTF2H5, which is active in NER (PubMed:9771713, PubMed:9852112). The core complex associates with the 3-subunit CDK-activating kinase (CAK) module composed of CCNH/cyclin H, CDK7 and MNAT1 to form the 10-subunit holoenzyme (holo-TFIIH) active in transcription (PubMed:9771713, PubMed:9852112). Interacts with GTF2H2 (p44) which stimulates the 5'-3' helicase activity of this subunit (PubMed:9771713). Component of the MMXD complex, which includes CIAO1, ERCC2, CIAO2B, MMS19 and SLC25A5 (PubMed:20797633). Interacts with CIAO1 and CIAO2B; the interaction WITH CIAO2B is direct (PubMed:23891004). Interacts with ATF7IP (PubMed:19106100). Interacts directly with MMS19 (PubMed:23585563). Part of TBP-based Pol II pre-initiation complex (PIC), in which Pol II core assembles with general transcription factors and other specific initiation factors including GTF2E1, GTF2E2, GTF2F1, GTF2F2, TCEA1, ERCC2, ERCC3, GTF2H2, GTF2H3, GTF2H4, GTF2H5, GTF2A1, GTF2A2, GTF2B and TBP; this large multi-subunit PIC complex mediates DNA unwinding and targets Pol II core to the transcription start site where the first phosphodiester bond forms.SUBUNIT (Microbial infection) Interacts with Epstein-Barr virus EBNA2.INTERACTION Interacts with GTF2H2/p44 via the C-terminus of this protein; mutations in the C-terminal region of XPD do not alter its helicase activity, but prevent its interaction with and helicase stimulation by GTF2H2/p44 (PubMed:9771713).PTM ISGylated.DISEASE The disease is caused by variants affecting the gene represented in this entry.DISEASE The disease is caused by variants affecting the gene represented in this entry.DISEASE The disease is caused by variants affecting the gene represented in this entry.SIMILARITY Belongs to the helicase family. RAD3/XPD subfamily.
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