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

Phospholipase C and two inositol polyphosphate (IP) kinases constitute a signaling pathway that regulates nuclear messenger RNA export through production of inositol hexakisphosphate (IP6). The inositol 1,4,5-trisphosphate kinase of this pathway in Saccharomyces cerevisiae, designated Ipk2, was found 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 required for gene regulation through ArgR-Mcm1. Thus, the phospholipase C pathway produces multiple IP messengers that modulate distinct nuclear processes. The results reveal a direct mechanism by which activation of IP signaling may control gene expression.