Involved in pre-mRNA splicing as component of the spliceosome. Involved in transcription-coupled repair (TCR), transcription and pre-mRNA splicing. Associates with RNA polymerase II, the TCR-specific proteins CKN1/CSA and ERCC6/CSB, and XPA. Identified in the spliceosome C complex. Component of the XAB2 complex, a multimeric protein complex composed of XAB2, PRPF19, AQR, ZNF830, ISY1, and PPIE. Identified in a pentameric intron-binding (IB) complex composed of AQR, XAB2, ISY1, ZNF830 and PPIE that is incorporated into the spliceosome as a preassembled complex. The IB complex does not contain PRPF19. Detected in the splicing complex carrying pre-mRNA. Belongs to the crooked-neck family.