Opposing post-translational modifications regulate Cep76 function to suppress centriole amplification

Abstract

Centrioles are critical for many cellular processes including cell division and cilia assembly. The number of centrioles within a cell is under strict control, and deregulation of centriole copy number is a hallmark of cancer. The molecular mechanisms that halt centriole amplification have not been fully elucidated. Here, we found that centrosomal protein of 76 kDa (Cep76), previously shown to restrain centriole amplification, interacts with cyclin-dependent kinase 2 (CDK2) and is a bona fide substrate of this kinase. Cep76 is preferentially phosphorylated by cyclin A/CDK2 at a single site S83, and this event is crucial to suppress centriole amplification in S phase. A novel Cep76 mutation S83C identified in a cancer patient fails to prevent centriole amplification. Mechanistically, Cep76 phosphorylation inhibits activation of polo-like kinase 1 (Plk1), thereby blocking premature centriole disengagement and subsequent amplification. Cep76 can also be acetylated, and enforced acetylation at K279 dampens the protein’s ability to inhibit amplification and precludes S83 phosphorylation. Acetylation of Cep76 normally occurs in G2 phase and correlates with loss of protein function. Our data suggest that temporal changes in posttranslational modifications of Cep76 during the cell cycle regulate its capacity to suppress centriole amplification, and its deregulation may contribute to malignancy.

Cep44 functions in centrosome cohesion by stabilizing rootletin

“…Immunoblotting and immunofluorescence were performed as described previously (Barbelanne et al, 2016). Briefly, cells were lysed in a lysis buffer (50 mM HEPES pH 7.4, 250 mM NaCl, 5 mM EDTA, 0.1% NP-40, 1 mM DTT, 0.1 M AEBSF, 2 μg/ml leupeptin, 2 μg/ml aprotinin, 10 mM NaF, 50 mM β-glycerophosphate and 10% glycerol) at 4°C for 30 min.…”

Implications of HBV-Driven Epigenetic Remodeling and Its Targets in Liver Cancer Stem Cells

“…Being critical for many cellular processes, centriole numbers are strictly controlled since increase in their copy number is considered among the hallmarks of cancer [25]. CEP76 appears to suppress centriole ampli cation suggesting that elevated miR3653 may contribute to the dormancy of liver CSCs via CEP76.…”

Building the right centriole for each cell type

“…In Cdk2-null cells, centrioles still duplicate; thus, if Cdk2 drives centriole duplication, its role can be overtaken by a redundant Cdk/cyclin combination. Contrary to its positive role in centriole formation, Cdk2 was proposed to play an inhibitory role in centriole reduplication via phosphorylation of Cep76 and inhibition of premature Plk1 activation ( Barbelanne et al, 2016 ). Cdk1 has been proposed to inhibit premature initiation of centriole formation in mitosis via its inhibitory binding and phosphorylation of STIL, which prevents both its presence at the centrosome and association with Plk4 ( Arquint and Nigg, 2014 ; Zitouni et al, 2016 ).…”