A Short Core Promoter Drives Expression of the ALF Transcription Factor in Reproductive Tissues of Male and Female Mice

The control of gene expression in reproductive tissues involves a number of unique germ cell-specific transcription factors. One such factor, ALF (TFIIA(tau)), encodes a protein similar to the large subunit of general transcription factor TFIIA. To understand how this factor is regulated, we characterized transgenic mice that contain the ALF promoter linked to either (beta)galactosidase or green fluorescent protein (GFP) reporters. The results show that as little as 133 base pairs are sufficient to drive developmentally accurate and cell-specific expression. Transgene DNA was methylated and inactive in liver, but could be reactivated in vivo by system administration of 5-aza, 2ʹ-deoxycytidine. Fluorescence-activated cell sorting allowed the identification of male germ cells that express the GFP transgene and provides a potential method to collect cells that might be under the control of a nonsomatic transcription system. Finally, we found that transcripts from the endogenous ALF gene and derived transgenes can also be detected in whole ovary and in germinal vesicle-stage oocytes of female mice. The ALF sequence falls into a class of germ cell promoters whose features include small size, high GC content, numerous CpG dinucleotides, and an apparent TATA-like element. Overall, the results define a unique core promoter that is active in both male and female reproductive tissues, and suggest mouse ALF may have a regulatory role in male and female gametogenic gene expression programs.