PAR polarity proteins are asymmetrically localized at the cortex of Caenorhabditis elegans zygotes. Seydoux and colleagues show that aPKC-mediated phosphorylation of PAR-2, which inhibits recruitment of PAR-2 to the cortex, is directly inhibited by microtubules emanating from the sperm-donated centrosomes. This protection allows PAR-2, and subsequently the PAR-1 kinase to access the cortex nearby the sperm, thus defining the posterior of the embryo. PAR-1 in turn phosphorylates PAR-3 to induce dissociation of PAR-3–aPKC from the posterior.
- Fumio Motegi
- Seth Zonies
- Geraldine Seydoux
