Previously, we characterized a rat cDNA for testisspecific transcription elongation factor S-II (SII-T1) (Q. Xu et al., J. Biol. Chem. 269, 3100–3103 (1994)). Here, we isolated a 335-bp fragment of the cDNA for mouse SII-T1, and used it to examine the expression of the SII-T1 gene in the testis by in situ hybridization. The results indicated that the SII-T1 gene is expressed exclusively in spermatocytes, showing no appreciable expression in spermatogonia, spermatids, or Leydig cells. RTPCR experiments using testis RNA from WI Wv mutant mice also suggested that SII-T1 is a specific transcription elongation factor essential for spermatogenesis.
