CHARACTERIZATION OF AN INTRONIC PROMOTER OF A CYCLIC ADENOSINE-3',5'-MONOPHOSPHATE (CAMP) - SPECIFIC PHOSPHODIESTERASE GENE THAT CONFERS HORMONE AND CAMP INDUCIBILITY

In the Sertoli cell, FSH stimulates transcription of a cAMP-phosphodie sterase (PDE) gene (PDE4D) and accumulation of corresponding mRNA and PDE protein. The regulation of this PDE gene is an important component of the desensitization state induced by this hormone. Given the ubiqu itous nature of this regulation controlling cAMP levels, the molecular basis for the PDE4D induction was further investigated. FSH stimulati on of the Sertoli cell causes the accumulation of only two of the four known PDE4D mRNAs (PDE4D1 and PDE4D2). The promoter controlling the e xpression of these two messages was identified and characterized. An E coRI fragment containing a coding exon as well as 5'-upstream sequence of the PDE4D1/2 mRNA was isolated from rat genomic libraries and sequ enced. No TATA box was identified, but CC-rich regions were present up stream of the putative translation start site. RNAse protection and PC R analysis indicated the presence of at least two distinct cap sites. This genomic region had promoter activity when transfected both in Ser toli and MA-10 cells. Deletion mutation indicated that basal promoter activity was contributed by regions upstream of both cap sites. Transc ription from this promoter was activated by FSH and (Bu)(2)cAMP, and e lements responsible for cAMP regulation were present upstream from the second cap site. These data demonstrate that an intronic promoter tha t is cAMP- and hormone-inducible directs the expression of these trunc ated PDE proteins.