Opi1 is a leucine zipper containing yeast transcription factor that negatively regulates phospholipid biosynthesis [2]. It represses the expression of several UAS(INO) cis acting element containing genes and its activity is mediated by phosphorylations catalysed by protein kinase A, protein kinase C and casein kinase II [1].

1: Casein kinase II phosphorylation of the yeast phospholipid synthesis transcription factor Opi1p. Chang YF, Carman GM; J Biol Chem. 2006; [Epub ahead of print] PMID:16407309

2: The OPI1 gene of Saccharomyces cerevisiae, a negative regulator of phospholipid biosynthesis, encodes a protein containing polyglutamine tracts and a leucine zipper. White MJ, Hirsch JP, Henry SA; J Biol Chem. 1991;266:863-872. PMID:1985968