Caenorhabditis elegans Elongin BC complex is essential for cell proliferation and chromosome condensation and segregation during mitosis and meiotic division II

Abstract

The ubiquitin-mediated protein degradation system is involved in a wide variety of cellular functions. The RING-H2 finger protein RBX1 is a common subunit of Cullin-based ubiquitin ligases. Caenorhabditis elegans RBX1 and CUL2 are essential for regulating chromosome condensation and segregation during mitosis and meiosis and are also critical for cell proliferation. Here, we demonstrate that Elongin B (ELB1) and C (ELC1) form a stable complex, and that depletion of either gene product by RNA-mediated interference (RNAi) causes pronounced defects in the second meiotic division. Embryos and adults that escape meiotic arrest have several irregular phenotypes. These include defects in mitotic chromosomal condensation and segregation, pronuclear rotation, and germ cell proliferation, abnormal cortical protrusion, and accumulation of the cyclin-dependent kinase inhibitor CKI1. All these defects are consistent with those found after depletion of CUL2. In addition, direct interaction between ELC1 and CUL2 is revealed by bacterial two-hybrid analysis. Thus, the RBX1/CUL2/ELC1/ELB1 complex acts as an E3 ubiquitin ligase in C. elegans and is essential for diverse functions relevant to chromosomal dynamics and cell cycle control.