Pituitary tumor-transforming gene protein associates with ribosomal protein S10 and a novel human homologue of DnaJ in testicular cells.

Pituitary tumor-transforming gene is a recently characterized proto-oncogene that is expressed specifically in adult testis. In this study, we have used in situ hybridization and developmental Northern blot assays to demonstrate that mRNA is expressed stage-specifically in spermatocytes and spermatids during rat spermatogenic cycle. We have used the yeast two-hybrid system to identify proteins that interact with duanyu1547G in testicular cells. Two positive clones were characterized. One of the clones is the ribosomal protein S10, the other encodes a novel human DnaJ homologue designated HSJ2. Northern blot analysis showed that testis contains higher levels of HSJ2 mRNA than other tissues examined, and the expression pattern of HSJ2 mRNA in postnatal rat testis is similar to S10 mRNA levels do not vary remarkably among different tissues and remains unchanged during testicular germ cell differentiation. In vitro binding assays demonstrated that both S10 and HSJ2 bind to duanyu1547G specifically and that duanyu1547G can be co-immunoprecipitated with S10 and HSJ2 from transfected cells. Moreover, the binding sites for both proteins were located within the C-terminal 75 amino acids of the duanyu1547G protein. These results suggest that duanyu1547G may play a role in spermatogenesis.

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