Combined Inactivation of Pocket Proteins and APC/CCdh1 by Cdk4/6 Controls Recovery from DNA Damage in G1 Phase.

Indra A Shaltiel,Lenno Krenning,René H Medema,Melinda Aprelia,Rob Klompmaker,Alba Llopis,Apostolos Menegakis

doi:10.3390/cells10030550

Indra A Shaltiel, Lenno Krenning + Show 5 more

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https://doi.org/10.3390/cells10030550

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Abstract

Most Cyclin-dependent kinases (Cdks) are redundant for normal cell division. Here we tested whether these redundancies are maintained during cell cycle recovery after a DNA damage-induced arrest in G1. Using non-transformed RPE-1 cells, we find that while Cdk4 and Cdk6 act redundantly during normal S-phase entry, they both become essential for S-phase entry after DNA damage in G1. We show that this is due to a greater overall dependency for Cdk4/6 activity, rather than to independent functions of either kinase. In addition, we show that inactivation of pocket proteins is sufficient to overcome the inhibitory effects of complete Cdk4/6 inhibition in otherwise unperturbed cells, but that this cannot revert the effects of Cdk4/6 inhibition in DNA damaged cultures. Indeed, we could confirm that, in addition to inactivation of pocket proteins, Cdh1-dependent anaphase-promoting complex/cyclosome (APC/CCdh1) activity needs to be inhibited to promote S-phase entry in damaged cultures. Collectively, our data indicate that DNA damage in G1 creates a unique situation where high levels of Cdk4/6 activity are required to inactivate pocket proteins and APC/CCdh1 to promote the transition from G1 to S phase.

Highlights

IntroductionPublisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations
D-type Cyclins bind to Cdk4 or Cdk6 during the G1-phase of the cell cycle, triggering the induction of expression of Cyclin
We have previously shown that the DNA damage response in G1 is lost in commonly used p53-proficient cancer cell lines [29], but is retained in immortalized non-transformed human retinal pigment epithelial cells (RPE-1) [26]

Summary

Introduction

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Cell division is a tightly regulated process to ensure proper organismal development and tissue homeostasis. Cyclins and their associated Cyclin-dependent kinases (Cdks) are the key regulators of the cell division cycle and their combined activity is associated with specific cell cycle transitions. D-type Cyclins bind to Cdk or Cdk during the G1-phase of the cell cycle, triggering the induction of expression of Cyclin

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