Isolation, physical characterization and expression analysis of the Saccharomyces cerevisiae positive regulatory gene PHO4.

The Saccharomyces cerevisiae PHO4 gene, which positively controls the expression of phosphatase genes, has been isolated by complementation of a pho4 mutation. The isolated DNA directed integration at the chromosomal PHO4 locus. The nucleotide sequence of PHO4 has a coding region of 930 nucleotides, flanked by sequences with typical transcription initiation and termination signals. The 5' region has characteristics of low-expression promoters and carries several uncommon elements, whose significance is not known. The predicted primary structure of the PHO4 protein, of 309 residues, does not show sequence elements typical of DNA-binding proteins. The transcription of PHO4 is independent of inorganic phosphate. Like other regulatory genes, PHO4 is transcribed at a very low level and the translation of its message uses preferentially several codons which are not employed for highly expressed genes.