THE PHOSPHORYLATION STATE OF THE 110-KDA COMPONENT OF THE YEAST SPINDLE POLE BODY SHOWS CELL-CYCLE-DEPENDENT REGULATION

The 110 kDa component of the yeast spindle pole body (SPB) encoded by the SPC110/NUF1 gene is an essential protein which is important for th e generation of a functional mitotic spindle in the yeast Saccharomyce s cerevisiae. Spc110p exists in a number of forms which differ in mobi lity upon separation by SDS-polyacrylamide gel electrophoresis. We sho w that this heterogeneity is due to differential phosphorylation on se rine or threonine residues and that Spc110p phosphorylation varies thr oughout the cell cycle. Specifically, the phosphorylated form of Spc11 0p appears as cells progress from S-phase and is coincident with the p resence of preanaphase mitotic spindles. Thus phosphorylation of Spc11 0p occurs at the stage in the cell cycle where SPBs acquire the compet ence to organize a mitotic spindle and could therefore represent an im portant regulatory event. (C) 1996 Academic Press, Inc.