THE RNA-BINDING PROTEIN, TB-RBP, IS THE MOUSE HORNOLOGUE OF TRANSLIN,A RECOMBINATION PROTEIN ASSOCIATED WITH CHROMOSOMAL TRANSLOCATIONS

The mouse RNA-binding protein, TB-RBP, suppresses translation in vitro and attaches mRNAs to microtubules by binding to conserved elements i n the 3' untranslated regions of specific mRNAs, We have now purified TB-RBP from testicular and brain cytoplasmic extracts and cloned its c DNA, We find that the mouse TB-RBP cDNAs contain an open reading frame of 228 amino acids with a leucine zipper domain within its C terminus , a transmembrane helix, and a group of putative phosphorylation sites , TB-RBP shows 99% identity to the human protein, translin, a recombin ation hotspot-binding protein associated with chromosomal translocatio ns [Aoki, K., Suzuki, K., Sugano, T., Tasaka, T., Nakahara, K., Kuge, O., Omori, A. & Kasai, M. (1995) Nat., Genet. 10, 167-174], As shown f or translin, TB-RBP also binds to single-stranded DNAs containing a br oad range of consensus sequences, many of which are similar to the Y a nd H RNA-binding sequences, Recombinant TB-RBP was synthesized and an antiserum was prepared against the recombinant protein, The identity b etween translin and TB-RBP was confirmed by demonstrating that immunop recipitation of TB-RBP from testicular extracts abolished formation of the RNA-TB-RBP complex, Based upon its DNA binding to target sequence s in clustered breakpoint regions, we propose that TB-RBP may be invol ved in DNA recombination or DNA repair in male germ cells.