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. Only expressed in spermatogonia and early spermatocytes, suggesting that expression is inactivated in the XY body during meiosis. The RBMY1 proteins are encoded by repeated regions of the Y chromosome. The exact number of functional copies is unclear and may vary between individuals, and some of them may represent pseudogenes. Overexpression of Rbmy proteins in mice carrying the Y(d1) deletion that removes most of the multi-copy Rbmy gene cluster does not have any effect and fails to reduce the frequency of abnormal sperm. These results raize the question of the role of Rbmy proteins in sperm development.