DEOXYRIBONUCLEIC-ACID PROTEIN INTERACTIONS ASSOCIATED WITH TRANSCRIPTIONAL INITIATION OF THE MOUSE TESTIS-SPECIFIC CYTOCHROME-C GENE

Transcriptional regulation of the mouse testis-specific cytochrome c ( cyt. c(T)) gene was studied by examining DNA-protein interactions in i ts proximal promoter. Testicular and liver nuclear proteins bound to t he cyt. c(T) gene at sites -105 to -81, +87 to +113, and +146 to +169, suggesting interactions with ubiquitous nuclear proteins. Protein pre sent in liver nuclear extracts bound to a fourth site at -176 to -125, whereas protein present in testicular nuclear extracts bound to a sub region of this site at -176 to -140. The sequence from -136 to -127, b ound by liver but not testicular nuclear proteins, is similar to that of the binding site of a somatic c-mos repressor protein. Lastly, diff erent nuclear proteins from mouse liver and testis bound to a region f rom -18 to +31 that contains a putative Y box at -13 to -2. Mobility s hift assays, Southwestern blots, and immunoprecipitation studies have established that this putative Y box binds a 52-kDa mouse testicular h omologue of the Xenopus germ cell-specific Y-box protein and a competi ng 50-kDa protein present in both liver and testis nuclear extracts. T hese data suggest that the testis-specific expression of the mouse cyt . c(T) gene during spermatogenesis may be regulated by the differentia l binding of tissue-specific nuclear proteins to its proximal promoter region.