Like checkpoints that monitor progression through mitosis, proper chromosome recombination and segregation during meiosis also require their own checkpoints. Bailis and Roeder demonstrate that modulating the phosphorylation state of the chromosome proteins Red1 and Mek1 regulates a meiotic checkpoint in yeast. Mek1 is known to phosphorylate Red1 during the pachetyne stage of meiosis, when double-stranded breaks and recombination events occur. The authors show that when Red1 is not dephosphorylated, cells arrest in pachytene. Because overexpression of the protein phosphatase Glc7 rescued mutant yeast that expressed constitutively activated Mek1 from meiotic arrest, the authors propose that phosphatase activity is needed to counterbalance kinase activity for progression through meiosis. This general phenomenon may hold true for regulation of other cell cycle checkpoints as well.
Bailis, J.M., and Roeder, G.S. (2000) Pachytene exit controlled by reversal of Mek1-dependent phosphorylation. Cell 101: 211-221. [Online Journal]