Abstract

A 34 base-pair (bp) fragment spanning sequences −154 to −120 of the promoter of the CHO1 gene (structural gene for phosphatidylserine synthase) from the yeast Saccharomyces cerevisiae has been shown to place transcription of a promoter-less Escherichia coll lacZ gene under control of the phospholipid precursors inositol and choline. Furthermore, in deletion experiments the CHO1 UAS ino was localized to sequences between −151 and −123 of the CHO1 promoter. A nine bp sequence was Identified in the promoter region of the CHO1 gene that shares an eight out of nine bp match with a sequence (consensus 5′ ATGTGAAAT 3′) that is repeated a total of 23 times upstream from several coregulated phospholipid biosynthetic genes. This sequence is contained within the −151 to −123 region to which the CHO1 UAS has been localized. The nine bp repeated element is believed to be Involved in the control of phospholipid biosynthetic gene transcription in response to changing levels of inositol and choline in the growth medium. This control has been shown to require activities encoded by the products of the three regulatory genes: INO2, INO4, and OPI1. A mutation in any of these regulatory genes results in aberrant CHO1-lacZ gene regulation, and affects regulation of the construct containing the 34 bp (−154 to −120) CHO1 fragment demonstrating that the regulatory signal generated by these genes interacts with the 5′ end of the CHO1 gene.

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