Involved in pre-mRNA splicing as component of spliceosome (PubMed:27185460, PubMed:18981222). As part of the spliceosome complex, plays a role in the regulation of spermatogonial differentiation (PubMed:27035939). When associated with the SAGA transcription regulatory histone acetylation (HAT) complex, might be involved in the transcriptional activation of a subset of SAGA-regulated genes (PubMed:27185460). Component of the SF3B complex (PubMed:27185460, PubMed:18981222). SF3B complex associates with the splicing factor SF3A complex and a 12S RNA unit to form the U2 small nuclear ribonucleoproteins complex (U2 snRNP)(PubMed:27185460, PubMed:18981222). Identified in the SAGA transcription regulatory histone acetylation (HAT) complex; the interaction is RNA-independent (PubMed:27185460). Lethal at the first instar larval stage (PubMed:27185460). RNAi-mediated knockdown in germ cells results in male sterility (PubMed:27035939). Belongs to the SF3B5 family.