Abstract
Sperm proteins that interact with zona pellucida 3 (ZP3) have not been clearly identified in humans. In the present study, the yeast two-hybrid (Y2H) system was used to identify human sperm proteins that interact with human ZP3. Human ZP3 cDNA was cloned into pAS2-1 yeast vector and used as bait to find reactive proteins in the human testis cDNA library. Six specific clones were obtained that were further confirmed for interaction using the mammalian two-hybrid system. These six clones showed homologies with several proteins in the GenBank database. Of these, the strongest ZP3-interacting protein, that shows 97% homology with ubiquitin associated protein-2 like (UBAP2L), was tested in the hemizona assay. UBAP2L antibodies significantly (p<0.001) inhibited human sperm-zona binding in this assay. We conclude that the Y2H system is a useful strategy for identifying novel genes encoding proteins that interact with ZP proteins. To our knowledge, this is the first study using the Y2H system to identify sperm proteins that interact with human oocyte ZP3. Novel proteins identified using this system may find applications in elucidating the fertilization cascade, development of a new generation of non-steroidal contraceptives, and specific diagnosis and treatment of human infertility.