Multiple elements influence transcriptional regulation from the human testis-specific PGK2 promoter in transgenic mice

The PGK2 gene is expressed in a strictly tissue-specific manner in meiotic spermatocytes and postmeiotic spermatids during spermatogenesis in eutherian mammals. Previous results indicate that this is regulated at the transcriptional level by core promoter sequences that bind ubiquitous transcription factors and by sequences in a 40-base pair (bp) upstream enhancer region (E1/E4) that bind tissue-specific transcription factors. Transgenic mice carrying different PGK2 promoter sequences linked to the chloramphenicol acetyltransferase (CAT) reporter gene, one containing only the 40-bp El/E4 enhancer sequence plus the core promoter and two containing 515 bp of PGK2 promoter but with either the El/E4 enhancer region or the Sp1- binding site in the core promoter disrupted by in vitro mutagenesis, all showed levels of expression reduced to less than half that of the wild-type 515 PGK2/CAT transgene. These results indicate that multiple factor-binding regions normally regulate initiation of transcription from the PGK2 promoter. The single disruption of any one of these binding activities reduced, but did not abolish, transgene expression. This is consistent with an 'enhanceosome'- like function in this promoter involving multiple bound activator proteins that interact in a combinatorial manner to synergistically promote testis- specific transcription.