Identification of two novel proteins that interact with germ-cell-specificRNA-binding proteins DAZ and DAZL1

The human DAZ (deleted in azoospermia) gene family on the Y chromosome and an autosomal DAZ-like gene, DAZL1, encode RNA-binding proteins that are exp ressed exclusively in germ cells. Their role in spermatogenesis is supporte d by their homology with a Drosophila male infertility gene boule and steri lity of Dazl1 knock-out mice. While all mammals contain a DAZL1 homologue o n their autosomes, DAZ homologues are present only on the Y chromosomes of great apes and Old World monkeys. The DAZ and DAZL1 proteins differ in the copy numbers of a DAZ repeat and the C-terminal sequences. We studied the i nteraction of DAZ and DAZL1 with other proteins as an approach to investiga te functional similarity between these two proteins. Using DAZ as bait in a yeast two-hybrid system, we isolated two DAZAP (DAZ-associated protein) ge nes. DAZAP1 encodes a novel RNA-binding protein that is expressed most abun dantly in the testis, and DAZAP2 encodes a ubiquitously expressed protein w ith no recognizable functional motif. DAZAP1 and DAZAP2 bind similarly to b oth DAZ and DAZL1 through the DAZ repeats. The DAZAP genes were mapped to c hromosomal regions 19p13.3 and 2q33-q34, respectively, where no genetic dis eases affecting spermatogenesis are known to map. (C) 2000 Academic Press.