A role for nuclear inositol 1,4,5-trisphosphate kinase in transcriptional control

Phospholipase C and two inositol polyphosphate (IP) kinases constitute a si gnaling pathway that regulates nuclear messenger RNA export through product ion of inositol hexakisphosphate (IP6). The inositol 1,4,5-trisphosphate ki nase of this pathway in Saccharomyces cerevisiae, designated Ipk2, was foun d to be identical to Arg82, a regulator of the transcriptional complex ArgR -Mcm1. Synthesis of inositol 1,4,5,6-tetrakisphosphate, but not IP6, was re quired for gene regulation through ArgR-Mcm1. Thus, the phospholipase C pat hway produces multiple IP messengers that modulate distinct nuclear process es. The results reveal a direct mechanism by which activation of IP signali ng may control gene expression.