Differentially expressed three non-coding alternate exons at 5' UTR of regulatory type I beta subunit gene of mouse.

Prkar1b gene encodes regulatory type I, beta subunit (RIβ) of cAMP dependent protein kinase A in mouse. Among the various isoforms of regulatory and catalytic subunits that comprise mammalian PKA, RIβ subunit is considered to be one of the important subunits for neuronal functions. This is involved in multiple forms of synaptic plasticity, and influences memory and learning by maintaining hippocampal long-term potentiation (LTP). Deficient expression of this gene has been implicated in autoimmune disease systemic lupus erythematosus (SLE). We have identified two novel non-coding exons of the Prkar1b gene (designated as exon 1A and exon 1B), which are spliced to the canonical exon 2 and constitute the 5' untranslated region giving rise to three alternative transcript isoforms. We have also confirmed the expression of the previously known first exon (designated as exon 1C) with known transcript published earlier. The transcripts containing exons 1A, 1B and 1C are differentially regulated during the development and tissue types. In silico study of more than 20 kb nucleotide sequence upstream of known translational initiation codon revealed three distinct promoter regions named as PA, PB, and PC upstream of the exon 1A, exon 1B and exon 1C respectively. PB is non-CpG related promoter but PA and PC are CpG related promoters, however all three promoters are TATA less. Further analysis showed that these promoters possess potential signature sequences for common as well as different transcription factors suggesting complex regulation of Prkar1b gene.