The double-life of the substrate-specific adaptor MEL-26

摘要

MEL-26 acts as a substrate-specific adaptor of CUL-3 E3 ligase in the early embryo of the nematode Caenorhabditis elegans. It recruits the microtubule-severing protein MEI-1 to the CUL-3 complex and therefore leads to the degradation of MEI-1 at the meiosis-to-mitosis transition. We found that MEL-26 plays a degradation-independent role in promoting the ingression of cleavage furrows. Consistent with this, lack of the mel-26-gene leads to defects in cytokinesis, such as slow ingression of furrows and regression. We identified the actin binding protein POD-1 as an interactor in a yeast two-hybrid screen using MEL-26 as bait. POD-1 is vital in localizing MEL-26 to the cortex, where the latter acts as an activator of cytokinesis. MEL-26 thus plays a dual role in the cell by (ⅰ) acting as a substrate-specifity factor in degradation of MEI-1 in concert with CUL-3, and (ⅱ) by activating cleavage-furrow activity in a degradation independent manner. The identification of MEL-26 as an activator of cytokinesis provides insight into the regulation of the cytoki-netic furrow, which has received little attention up until now.