CDC-25.2, a <i>C. elegans</i> ortholog of <i>cdc25</i>, is essential for the progression of intestinal divisions

Intestinal divisions in <i>Caenorhabditis elegans</i> take place in 3 stages: (1) cell divisions during embryogenesis, (2) binucleations at the L1 stage, and (3) endoreduplications at the end of each larval stage. Here, we report that CDC-25.2, a <i>C. elegans</i> ortholog of Cdc25, is required for these specialized division cycles between the 16E cell stage and the onset of endoreduplication. Results of our genetic analyses suggest that CDC-25.2 regulates intestinal cell divisions and binucleations by counteracting WEE-1.3 and by activating the CDK-1/CYB-1 complex. CDC-25.2 activity is then repressed by LIN-23 E3 ubiquitin ligase before the onset of intestinal endoreduplication, and this repression is maintained by LIN-35, the <i>C. elegans</i> ortholog of Retinoblastoma (Rb). These findings indicate that timely regulation of CDC-25.2 activity is essential for the progression of specialized division cycles and development of the <i>C. elegans</i> intestine.