The CHK-2 antagonizing phosphatase PPM-1.D regulates meiotic entry via catalytic and non-catalytic activities

The transition from the stem cell/progenitor fate to meiosis is mediated by several redundant post-transcriptional regulatory pathways in C. elegans. Interfering with all three branches causes tumorous germlines. SCFPROM-1 comprises one branch and mediates a scheduled degradation step at entry into meiosis. prom-1 mutants show defects in timely initiation of events of meiotic prophase I, resulting in high rates of embryonic lethality. Here, we identify a crucial substrate for PROM-1, encoded by the phosphatase PPM-1.D/Wip1. We report that it antagonizes CHK-2 kinase, a key regulator for meiotic prophase initiation e.g., DNA double strand breaks, chromosome pairing and synaptonemal complex formation. We propose that PPM-1.D controls the amount of active CHK-2 by both catalytic and non-catalytic activities, where strikingly the non-catalytic regulation seems to be crucial at meiotic entry. PPM-1.D sequesters CHK-2 at the nuclear periphery and programmed SCFPROM-1 mediated degradation of PPM-1.D liberates the kinase and promotes meiotic entry.