Regulation of the Saccharomyces cerevisiae CKI1-encoded choline kinase by zinc depletion

Abstract

In the yeast Saccharomyces cerevisiae, the CKI1-encoded choline kinase catalyzes the committed step in the synthesis of phosphatidylcholine via the CDP-choline branch of the Kennedy pathway. Analysis of a PCKI1-lacZ reporter gene revealed that CKI1 expression was regulated by intracellular levels of the essential mineral zinc. Zinc depletion resulted in a concentration-dependent induction of CKI1 expression. This regulation was mediated by the zinc-sensing and zinc-inducible transcriptional activator Zap1p. A purified Zap1p probe interacted with two putative UASZRE sequences (ZRE1 and ZRE2) in the CKI1 promoter. Mutations of ZRE1 and ZRE2 to a nonconsensus UASZRE attenuated the induction of CKI1 expression in response to zinc depletion. A UASINO element in the CKI1 promoter was responsible for stimulating CKI1 expression, but this element was not involved with the regulation by zinc depletion. The induction of CKI1 expression in zinc-depleted cells translated into increased choline kinase activity in vitro and in vivo, and an increase in phosphatidylcholine synthesis via the Kennedy pathway. © 2008 by The American Society for Biochemistry and Molecular Biology, Inc.