CDK4 protein is degraded by anaphase-promoting complex/cyclosome in mitosis and reaccumulates in early G1 phase to initiate a new cell cycle in HeLa cells

Huabo Chen; Xiaowei Xu; Guopeng Wang; Boyan Zhang; Gang Wang; Guangwei Xin; Junjun Liu; Qing Jiang; Hongyin Zhang; Chuanmao Zhang

doi:10.1074/jbc.M116.773226

CDK4 protein is degraded by anaphase-promoting complex/cyclosome in mitosis and reaccumulates in early G₁ phase to initiate a new cell cycle in HeLa cells

From the ^‡Ministry of Education Key Laboratory of Cell Proliferation and Differentiation and the State Key Laboratory of Membrane Biology, College of Life Sciences, Peking University, Beijing 100871, China,
the ^¶Cancer Research Center, Peking University Hospital, Peking University, Beijing 100871, China, and
the ^§Department of Biological Sciences, California State Polytechnic University, Pomona, California 91768

↵2 To whom correspondence may be addressed. Tel.: 86-10-62757173; E-mail: jiangqing{at}pku.edu.cn.
↵3 To whom correspondence may be addressed. Tel.: 86-10-62757173; E-mail: zhangcm{at}pku.edu.cn.

↵1 These authors contributed equally to this work.
Edited by Xiao-Fan Wang

Abstract

CDK4 regulates G₁/S phase transition in the mammalian cell cycle by phosphorylating retinoblastoma family proteins. However, the mechanism underlying the regulation of CDK4 activity is not fully understood. Here, we show that CDK4 protein is degraded by anaphase-promoting complex/cyclosome (APC/C) during metaphase-anaphase transition in HeLa cells, whereas its main regulator, cyclin D1, remains intact but is sequestered in cytoplasm. CDK4 protein reaccumulates in the following G₁ phase and shuttles between the nucleus and the cytoplasm to facilitate the nuclear import of cyclin D1. Without CDK4, cyclin D1 cannot enter the nucleus. Point mutations that disrupt CDK4 and cyclin D1 interaction impair the nuclear import of cyclin D1 and the activity of CDK4. RNAi knockdown of CDK4 also induces cytoplasmic retention of cyclin D1 and G₀/G₁ phase arrest of the cells. Collectively, our data demonstrate that CDK4 protein is degraded in late mitosis and reaccumulates in the following G₁ phase to facilitate the nuclear import of cyclin D1 for activation of CKD4 to initiate a new cell cycle in HeLa cells.

Footnotes

This work was supported by National Natural Science Foundation of China (NSFC) Grants 31371365, 31520103906, and 31430051 and Ministry of Science and Technology of China Grants 2016YFA0100501 and 2016YFA0500201. The authors declare that they have no conflicts of interest with the contents of this article.
This article contains supplemental Table 1, Figs. S1–S3, and Movies 1–7.