Involved in pre-mRNA splicing as component of the spliceosome (PubMed:11991638, PubMed:25599396, PubMed:28502770, PubMed:28076346). Intron-binding spliceosomal protein required to link pre-mRNA splicing and snoRNP (small nucleolar ribonucleoprotein) biogenesis (PubMed:16949364). Plays a key role in position-dependent assembly of intron-encoded box C/D small snoRNP, splicing being required for snoRNP assembly (PubMed:16949364). May act by helping the folding of the snoRNA sequence. Binds to intron of pre-mRNAs in a sequence-independent manner, contacting the region between snoRNA and the branchpoint of introns (40 nucleotides upstream of the branchpoint) during the late stages of splicing (PubMed:16949364). Has ATP-dependent RNA helicase activity and can unwind double-stranded RNA molecules with a 3' overhang (in vitro) (PubMed:25599396). ATP + H2O = ADP + H(+) + phosphate Identified in the spliceosome C complex (PubMed:11991638, PubMed:16949364, PubMed:25599396, 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). Within the spliceosome, interacts with SNRPA1, SF3B1, SF3B3, SF3A1 and SF3A2 (PubMed:25599396). Localizes to speckle-like regions of the nucleoplasm. Contains an N-terminal domain with structural similarity to ARM repeat regions; this domain functions as scaffold for protein-protein interactions, but is not required for RNA binding or for ATP-dependent RNA helicase activity. Belongs to the CWF11 family. Extended N-terminus.