The C-elegans E2F-and DP-related proteins are required for embryonic asymmetry and negatively regulate Ras/MAPK signaling

Early C. elegans embryos exhibit protein asymmetries that allow rapid diver sification of cells. Establishing these asymmetries requires the novel prot ein MEX-5. We show that mutations in the efl-1 and dpl-1 genes cause defect s in protein localization resembling defects caused by mutations in mex-5. efl-1 and dpl-1 encode homologs of vertebrate E2F and DP proteins that regu late transcription as a heterodimer. efl-l and dpl-1 mutants have elevated levels of activated Map kinase in oocytes. Their mutant phenotype and that of mex-5 mutants can be suppressed by reducing Ras/Map kinase signaling. We propose this signaling pathway has a role in embryonic asymmetry and that EFL-1/DPL-1 control the level of Map kinase activation.