Identification of the testis c-mos promoter: specific activity in a seminiferous tubule-derived extract and binding of a testis-specific nuclear factor.

The c-mos proto-oncogene is predominantly expressed in male and female germ cells and is involved in the regulation of meiosis. To investigate the mechanism of testis-specific regulation of c-mos transcription, I set out to identify the rat testis c-mos promoter. This was achieved by characterization of the rat testis c-mos transcription start site by primer extension and sequence analysis of cDNAs obtained by polymerase chain reaction amplification of 5' ends of c-mos RNA. The rat testis c-mos transcription start site is located 0.56 kb upstream of the coding region. A fragment containing the rat testis c-mos promoter directs transcription in a nuclear extract derived from rat seminiferous tubules, but not in a liver nuclear extract. DNAase I footprint analysis and gel-retardation assays showed binding of a novel testis-specific nuclear factor to the rat testis c-mos promoter at a site homologous to the testis-specific cis-acting element identified in the promoter of the RT7 gene, which is specifically expressed in haploid male germ cells.