Expression of the nuclear RING finger protein SNURF/RNF4 during rat testis development suggests a role in spermatid maturation.

A small nuclear RING finger protein, termed SNURF (or RNF4), is a coregulator of androgen receptor-dependent transcription. To elucidate the physiological role of SNURF in vivo, cell type-specific localization and changes in SNURF mRNA and protein accumulation were followed during testicular development and spermatogenesis of the rat. Two SNURF transcripts, approximately 3.0 and 1.6 kb in size, were detected in adult rat testis. Both mRNA species are capable of encoding full-length SNURF protein. The 3.0 kb SNURF mRNA is persistently expressed in Sertoli cells of both immature and mature testes, whereas the expression of the 1.6 kb transcript appears after day 30 of postnatal life and is restricted to step 4-11 spermatids. Increased accumulation of SNURF in step 4-11 spermatids, which do not express the androgen receptor, indicates that SNURF action is not restricted to the regulation of androgen signaling. Germ cell expression of SNURF coincides with the last transcriptional activity of the haploid genome and alterations in chromatin structure, suggesting that SNURF is involved in the regulation of processes required for late steps of spermatid maturation.