The possible functional significance of phosphatidylinositol in G1 arrest of Saccharomyces cerevisiae

Individual phospholipids were assayed in exponentially growing and G₁-arrested temperature-sensitive cell division cycle (cdc) mutants of Saccharomyces cerevisiae. It was observed that cdc28 cells which are known to arrest at ‘start’ when shifted to their non-permissive temperature, resulted in a 40% decrease in phosphatidylinositol (PI) level while the phosphatidylserine (PS) content was doubled in these cells. The reduced level of PI was restored in cdc4 and cdc7 mutants which are known to arrest past the ‘start’. The increase in PS level in cdc8 mutant which was probably to compensate the intrinsic charging of membrane environment, was also reduced in cdc4 and cdc7 mutants. Our results demonstrate that PI may play a role in yeast cell division and growth that the abnormalities of cdc28 could also be related to PI decrease.