Crosstalk of prolyl isomerases, Pin1/Ess1, and cyclophilin A

Previous studies have indicated that Ess1/Pin1, a gene in the parvulin fami ly of peptidyl-prolyl isomerases (PPIases), plays an important role in regu lating the G(2)/M transition of the cell cycle by binding cell-cycle-regula ting proteins in eukaryotic cells. Although the ess1 gene has been consider ed to be essential in yeast, we have isolated viable ess1 deletion mutants and demonstrated, via analysis of yeast gene expression profiles using micr oarray techniques, a novel regulatory role for ESS1 in the G(1) phase. Alth ough the overall expression profiles in the tested strains (C110-1, W303, S 288c, and RAY-3AD) were similar, marked changes were detected for a number of genes involved in the molecular action of ESS1. Among these, the express ion levels of a cyclophilin A gene, also a member of the PPIase family, inc reased in the ess1 null mutant derived from C110-1. Subsequent treatment wi th cyclosporin A significantly retarded growth, which suggests that ESS1 an d cyclophilin A are functionally linked in yeast cells and play important r oles at the G(1) phase of the cell cycle. (C) 2001 Academic Press.