Cell cycle arrest induced by trichoplein depletion is independent of cilia assembly.

Cilia assembly and centriole duplication are closely coordinated with cell cycle progression, and inhibition of cilia disassembly impedes cell cycle progression. The centrosomal protein trichoplein (TCHP) has been shown to promote cell cycle progression in the G 1 -S phase by disassembling cilia. In this study, we showed that deletion of TCHP not only prevented the progression to the S phase but also resulted in cell cycle exit and entrance into G 0 phase. Surprisingly, we found that loss of TCHP-induced G 0 arrest could not be reversed by blocking the assembly of cilia. In cells without IFT20 or CEP164, two genes encoding key factors for ciliogenesis, depletion of TCHP still led to G 0 arrest. Mechanistically, we also found that TCHP depletion-induced cell cycle arrest was not mediated through a centrosome surveillance mechanism, but inhibition of Rb or concomitant inhibition of both Rb and p53 signaling pathways was required to reverse the cell cycle phenotype. In conclusion, our study provides new insights into the function of TCHP in cell cycle progression.