RBMY, a probable human spermatogenesis factor, and other hnRNP G proteins interact with Tra2 beta and affect splicing

The RBMY gene family is found on the Y chromosome of all mammals, and micro deletions are strongly associated with infertility in men. RBMY expresses R BM only in the nuclei of germ cells, whereas its X chromosome homologue, RB MX, expresses hnRNP G ubiquitously. We show here that RBM, hnRNP G and a no vel testis-specific relative, termed hnRNP G-T, interact with Tra2 beta, an activator of pre-mRNA splicing that is ubiquitous but highly expressed in testis. Endogenous hnRNP G and Tra2 beta proteins are associated in HeLa nu clear extracts. RBM and Tra2 beta co-localize in two major domains in human spermatocyte nuclei. Phosphorylation enhanced the interaction and reduced competing RNA binding to the interaction domains. Incubation with the prote in interaction domain of RBM inhibited splicing in vitro of a specific pre- mRNA substrate containing an essential enhancer bound by Tra2 beta. The RNA -binding domain of RBM affected 5' splice site selection. We conclude that the hnRNP G family of proteins is involved in pre-mRNA splicing and infer t hat RBM may be involved in Tra2 beta-dependent splicing in spermatocytes.