The SNARE-associated component SNAPIN binds PUMILIO2 and NANOS1 proteins in human male germ cells

It has been reported that a highly conserved human protein PUMILIO2 forms a complex with NANOSI in human male germ cells, as does the Drosophila ancestor Pumilio, which binds Nanos to regulate translation of specific mRNAs. Here, we found that PUMILIO2 interacts also with SNAPIN, a modulator of SNARE complex assembly, which is involved in vesicle trafficking. We demonstrated that SNAPIN interacts additionally with NANOSI protein. This is the first report demonstrating that the N-terminal region of NANOSI is necessary for protein binding. In human testis, SNAPIN co-localizes with PUMILIO2 and NANOSI in prenatal and also in spermatogenic germ cells of the adult. We describe for the first time the expression of SNAPIN in germ cells which raises possibility that SNAPIN plays an extra role in mammals which is germ cell specific. The presence of a coiled-coil domain responsible for protein-protein interaction could enable SNAPIN to be an adaptor of PUMILIO2 and NANOSI, binding other factors to regulate translation in the development of the human germ cells.