Both isoforms of the cAMP-dependent protein kinase catalytic subunit can activate transcription of the prolactin gene.

Whereas molecular cloning experiments have provided evidence for the presence of two closely related genes for the catalytic subunit of the cAMP-dependent protein kinase, the possible interchangeability of these isoforms in initiating biological processes has not been examined. To test the role of the two forms of the kinase in regulating transcription, expression vectors containing the coding sequence of either kinase have been cotransfected with a fusion gene containing the prolactin promoter coupled to an appropriate marker gene. The results demonstrate that expression vectors for both isoforms of the catalytic subunit are able to increase prolactin promotor activity in a dose-dependent manner. The effects can be observed by measuring either marker gene activity or RNA levels. Transfection of an expression vector encoding an inactive catalytic subunit did not stimulate prolactin promoter activity. The results provide additional evidence for the role of the catalytic subunit of the cAMP-dependent kinase in mediating regulation of specific gene transcription and demonstrate that both forms of the catalytic subunit are capable of participating in the regulation of transcription.