Co-regulation with genes of phospholipid biosynthesis of the CTR/HNM1-encoded choline/nitrogen mustard permease in Saccharomyces cerevisiae.

An 815 bp region of the promoter of the Saccharomyces cerevisiae gene CTR/HNM1, encoding choline permease was sequenced and its regulatory function analysed by deletion studies in an in-frame promoter-lacZ construct. In addition to the TATA box, a 10 bp motif (consensus 5'-CATGTGAAAT-3') was found to be mandatory for CTR/HNM1 expression. This 'decamer' motif is located between nucleotides -262 and -271 and is identical in 9 of 10 bp with the regulatory motif found in the S. cerevisiae INO1 and CHO1 genes. Constructs with the 10 bp sequence show high constitutive expression, while elimination or alterations at three nucleotide positions, of the decamer motif in the context of an otherwise unchaged promoter leads to total loss of beta-galactosidase production. Expression of the CTR/HNM1 gene in wild-type cells is regulated by the phospholipid precursors inositol and choline; no such influence is seen in cells bearing mutations in the phospholipid regulatory genes INO2, INO4, and OPI1. There is no regulation by INO2 and OPI1 in the absence of the decamer motif. However constructs not containing this sequence (promoter intact to positions -213 or -152) are still controlled by INO4. Other substrates of the choline permease, i.e. ethanolamine, nitrogen mustard and nitrogen half mustard do not regulate expression of CTR/HNM1.