The Testicular Specific Protein Ggn1 Of Ggnbp2 The Interaction

Germ-cell deficient (gcd) mouse is a mutant manifesting infertility at adulthood, which served as a mouse model for the sertoli-cell-only syndrome in male and premature ovarian failure (POF) disease in female[1]. Recently it was found that FancL (originally called Pog) was the gene underlying gcd mutation[2,3]. FANCL was then found to be an ubiquitin E3 ligase, which is involved in DNA damage repair[4-6]. It was recently found that a novel germ cell-specific gene Ggn (Gametogenetin) encoding products, GGNl and GGN3 interacting with FANCL[7]. Ggn encoded 3 putative proteins, gametogenetin protein 1 (GGNl), gametogenetin protein 2 (GGN2) and gametogenetin protein 3 (GGN3) by alternative splicing. GGN3 and GGNl C-termini are completely identical.The spatial and temporal expression of Ggn mRNA in the testis indicated that this gene might serve important role in spermatogenesis. Despite the finding that GGNl interacted with FANCL, the cellular pathway GGNl is involved in remained unknown. Finding more interacting partners of GGNl, especially the interacting partners with known function, will be helpful for the study of the function of GGNl and will also benefit our understanding of spermatogenesis[7].We used the yeast two-hybrid system to screen adult testis libraries to look for GGNl interacting proteins. Different regions of GGNl were used as the bait. After several screens we identified three proteins, GGNBP1, GGNBP2 and OAZ3 as the potential interaction partners of GGNl. We prepared the high-specificity polyclonal antibody of GGNBP2 and GGN3. The N-terminal 400 amino acid residues of GGNBP2 were enough to mediate the interaction with the C-terminal 82 amino acid residues of GGNl. The interaction between the two proteins was further confirmed by co-localization and coimmunoprecipitation experiments. Both proteins were post-translationally modified resulting in much more larger molecular weight than expected[8].