Essential factor involved in transcription-coupled nucleotide excision repair which allows RNA polymerase II-blocking lesions to be rapidly removed from the transcribed strand of active genes (By similarity). Upon DNA-binding, it locally modifies DNA conformation by wrapping the DNA around itself, thereby modifying the interface between stalled RNA polymerase II and DNA (By similarity). It is required for transcription-coupled repair complex formation. It recruits the CSA complex (DCX(ERCC8) complex), nucleotide excision repair proteins and EP300 to the sites of RNA polymerase II-blocking lesions (By similarity). Plays an important role in regulating the choice of the DNA double-strand breaks (DSBs) repair pathway and G2/M checkpoint activation; DNA-dependent ATPase activity is essential for this function (By similarity). Regulates the DNA repair pathway choice by inhibiting non-homologous end joining (NHEJ), thereby promoting the homologous recombination (HR)-mediated repair of DSBs during the S/G2 phases of the cell cycle (By similarity). Mediates the activation of the ATM- and CHEK2-dependent DNA damage responses thus preventing the premature exit from the G2/M checkpoint (By similarity). Acts as a chromatin remodeler at DSBs; DNA-dependent ATPase-dependent activity is essential for this function (By similarity). Remodels chromatin by evicting histones from chromatin flanking DSBs, limiting RIF1 accumulation at DSBs thereby promoting BRCA1-mediated HR (By similarity). Required for stable recruitment of ELOA and CUL5 to DNA damage sites (By similarity). Involved in UV-induced translocation of ERCC8 to the nuclear matrix (By similarity). Essential for neuronal differentiation and neuritogenesis; regulates transcription and chromatin remodeling activities required during neurogenesis (By similarity). ATP + H2O = ADP + H(+) + phosphate Homodimer (By similarity). Binds DNA (By similarity). Interacts with ERCC8 (By similarity). Interacts with RNA polymerase II; interaction is enhanced by UV irradiation (By similarity). Component of the B-WICH complex, at least composed of SMARCA5/SNF2H, BAZ1B/WSTF, SF3B1, DEK, MYO1C, ERCC6, MYBBP1A and DDX21 (By similarity). Interacts with KIAA1530/UVSSA (By similarity). Interacts with ELOA and CUL5; the interaction is induced by DNA damaging agents or by inhibitors of RNA polymerase II elongation (By similarity). Interacts (via WHD region) with RIF1 (By similarity). Interacts with SMARCC2/BAF170, SMARCB1/BAF47 and the neuron-specific chromatin remodeling complex (nBAF complex) (By similarity). Interacts with ERCC5/XPG (via C-terminus); the interaction stimulates ERCC6/CSB binding to DNA repair bubble and ERCC6/CSB ATPase activity (By similarity). May form a complex composed of RNA polymerase II, ERCC6/CSB and ERCC5/XPG which associates with the DNA repair bubble during transcription-coupled nucleotide excision repair (By similarity). Interacts with CAND1, CSTF1, DDX3X, DDX5, DDX17, DDX23, DHX36, HDAC1, HNRNPU, MTA2, PRPF3, PSMD3, RBBP4, SFPQ, SMARCA1, SMARCA2, TOP1, USP7 and XRCC5 (By similarity). A C-terminal ubiquitin-binding domain (UBD) is essential for transcription-coupled nucleotide excision repair activity, interaction with RNA polymerase II, association with chromatin after UV irradiation and for mediating the UV-induced translocation of ERRC8 to the nuclear matrix. The N-terminal domain exerts an inhibitory effect on the helicase ATP-binding domain in such a manner that its ATPase activity is restricted (By similarity). Phosphorylation at Ser-158 promotes the intramolecular interaction of the N-terminal domain with the helicase ATP-binding domain, thereby probably releasing the inhibitory effect of the N-terminal domain on its ATPase activity (By similarity). Phosphorylated in a cell cycle-dependent manner at Ser-158 by cyclin A-CDK2 in response to DNA damage (By similarity). Phosphorylation at this site promotes the intramolecular interaction of the N-terminal domain with the helicase ATP-binding domain, thereby probably releasing the inhibitory effect of the N-terminal domain on its ATPase activity (By similarity). Phosphorylation is essential for its chromatin remodeling activity (By similarity). Ubiquitinated at the C-terminus (By similarity). Ubiquitination by the CSA complex leads to ERCC6 proteasomal degradation in a UV-dependent manner (By similarity). Stabilized following interaction with KIAA1530/UVSSA, which promotes recruitment of deubiquitinating enzyme USP7, leading to deubiquitination of ERCC6 thereby preventing UV-induced degradation of ERCC6 by the proteasome (By similarity). Belongs to the SNF2/RAD54 helicase family.