RNA-binding protein involved in pre-mRNA splicing. Required for sperm development. Acts additively with TRA2B to promote exon 7 inclusion of the survival motor neuron SMN. Binds non-specifically to mRNAs. Interacts with splicing factor proteins SFRS3/SRP20, TRA2B/SFRS10, KHDRBS1/SAM68 and KHDRBS3. Testis-specific. Expressed in all of the transcriptionally active stages of germ cell development from spermatogonia through spermatocytes to round spermatids. The RBMY1 proteins are encoded by repeated regions of the Y chromosome, mostly within the AZFb region. The exact number of functional copies is unclear and may vary between individuals, and some of them may represent pseudogenes. The proteins are very similar, which makes the characterization of each protein difficult. Thus, most experiments do not discriminate between the different members. One can therefore suppose that reported interactions with a RBMY1 protein involve all the proteins.