Involved in pre-mRNA splicing as component of the spliceosome (PubMed:11991638, PubMed:28502770, PubMed:28076346). Involved in transcription-coupled repair (TCR), transcription and pre-mRNA splicing (PubMed:10944529, PubMed:17981804). Associates with RNA polymerase II, the TCR-specific proteins CKN1/CSA and ERCC6/CSB, and XPA (PubMed:10944529). Identified in the spliceosome C complex (PubMed:11991638, PubMed:28502770, PubMed:28076346). Component of the XAB2 complex, a multimeric protein complex composed of XAB2, PRPF19, AQR, ZNF830, ISY1, and PPIE (PubMed:17981804). 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 (PubMed:25599396). The IB complex does not contain PRPF19 (PubMed:25599396). Detected in the splicing complex carrying pre-mRNA. Belongs to the crooked-neck family. Extended N-terminus. Alternative splicing. Incomplete sequence.