ERCC3

ATP-dependent 3'-5' DNA helicase/translocase. Binds dsDNA rather than ssDNA, unzipping it in a translocase rather than classical helicase activity. 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. The ATPase activity of XPB/ERCC3, but not its helicase activity, is required for DNA opening; it may wrap around the damaged DNA wedging it open, causing localized melting that allows XPD/ERCC2 helicase to anchor. 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/ERCC3 is required for promoter opening and promoter escape. In transcription pre-initiation complexes induces and propagates a DNA twist to open DNA. Also involved in transcription-coupled nucleotide excision repair (NER) of damaged DNA. 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 structure of the TFIIH transcription complex differs from the NER-TFIIH complex; large movements by XPD/ERCC2 and XPB/ERCC3 are stabilized by XPA. XPA retains XPB/ERCC3 at the 5' end of a DNA bubble (mimicking DNA damage)..

Function from UniProtKB (P19447), read 2026-09-23. CC BY 4.0.