Structural features of the murine gene encoding the RIβ subunit of cAMP-dependent protein kinase

The activation of cyclic AMP-dependent protein kinase is controlled by the regulatory (R) subunits of the holo-enzyme. Here we present a characterization of the mouse RIβ subunit gene, which in contrast to other subunit genes of cyclic AMP-dependent protein kinase is expressed almost exclusively in neurons. It was determined that RIβ is relatively large with 11 exons spanning a minimum 75 kb. The mouse chromosomal locus (designated Prkar1b) was determined by interspecific backcross mapping and found to reside on the distal arm of chromosome 5. Previously, it was shown that 3.5 kb of DNA encompassing the RIβ promoter could direct neural-specific gene expression in transgenic mice. Analysis of this DNA suggests the presence of an unusually large number of binding sites for transcription factors ranging from tissue-specific regulators, immediate-early genes, and mediators of hormone action. In addition to 18 putative SP1 sites, we identified 27 consensus sequences for basic Helix-Loop-Helix, POU, and Pax family members, 5 AP1 sites, and over 40 half-sites for the superfamily of steroid hormone receptor. Gel mobility-shift assays employing brain nuclear extract and pure transcription factor protein established that many of these DNA sequences are functional in binding protein. The abundance and configuration of transcription factor binding sites within the promoter region of RIβ suggests that this gene is subject to complex modes of regulation in neurons.