Rootletin prevents Cep68 from VHL-mediated proteasomal degradation to maintain centrosome cohesion

Abstract

Centrosome cohesion, mostly regarded as a proteinaceous linker between parental centrioles, ensures the interphase centrosome(s) to function as a single microtubule-organizing center. Maintenance of centrosome cohesion counts on a number of centrosomal linker proteins because depletion of any of those leads to premature centrosome separation in interphase, termed centrosome splitting. However, the underlying mechanisms of the dependence are unknown. Here, we show that absence of Rootletin triggers the von Hippel-Lindau tumour suppressor protein (VHL)-mediated proteasomal degradation of Cep68 and, in turn, results in centrosome splitting. The VHL E3 ligase complex ubiquitinates Cep68 in vitro and in vivo. Co-silencing of Rootletin and VHL reverts Cep68 loss and centrosome splitting. Expression of a stable mutant of Cep68, either diminishing its polyubiquitylation or eliminating binding to β-domain of VHL, also suppresses centrosome splitting provoked by Rootletin depletion. We propose that the archetypal linker protein Rootletin maintains centrosome cohesion in part through inhibition of VHL-mediated Cep68 degradation.

Keywords: Centrosome cohesion; Centrosome splitting; Cep68; Rootletin; Ubiquitin-proteasome system (UPS); von Hippel-Lindau (VHL).