DISTRIBUTION OF TENR, AN RNA-BINDING PROTEIN, IN A LATTICE-LIKE NETWORK WITHIN THE SPERMATID NUCLEUS IN THE MOUSE

In a molecular screen for cDNAs that encode protamine RNA-binding prot eins, we obtained seven independent clones that encode Tenr, a testis nuclear RNA-binding protein. Tenr is a 72-kDa protein that has one cop y of a previously described RNA-binding domain. Northwestern blotting experiments showed that a maltose-binding protein-Tenr fusion binds to a variety of RNAs in vitro and that it does not bind to single-strand ed or double-stranded DNA. The Tenr gene is transcribed exclusively in the testis, and its mRNA is restricted to cells from the pachytene sp ermatocyte stage through the round spermatid stage. Immuno-localizatio n of the Tenr protein within the testis showed that it is first detect ed postmeiotically, demonstrating that the Tenr mRNA is under translat ional control. The Tenr protein is localized to round and early elonga ting spermatid cells, and confocal microscopy revealed a lattice-like nuclear distribution suggesting association with the nuclear scaffold. We suggest that the Tenr protein may be involved in testis-specific n uclear posttranscriptional processes such as heterogeneous nuclear RNA (hnRNA) packaging, alternative splicing, or nuclear/cytoplasmic trans port of mRNAs.