TIAR marks nuclear G2/M transition granules and restricts CDK1 activity under replication stress.

Vanesa Lafarga,Anne‐Laure Pauleau,Andres J Lopez‐Contreras,Georg Stoecklin,Lea Roessig,Oliver J Gruss,Juan Mendez,Katharina Haneke,Sara Rodriguez‐Acebes,Oscar Fernandez‐Capetillo,Hsu‐Min Sung,Marius Bruer,Sylvia Erhardt

doi:10.15252/embr.201846224

Abstract

The G2/M checkpoint coordinates DNA replication with mitosis and thereby prevents chromosome segregation in the presence of unreplicated or damaged DNA. Here, we show that the RNA‐binding protein TIAR is essential for the G2/M checkpoint and that TIAR accumulates in nuclear foci in late G2 and prophase in cells suffering from replication stress. These foci, which we named G2/M transition granules (GMGs), occur at low levels in normally cycling cells and are strongly induced by replication stress. In addition to replication stress response proteins, GMGs contain factors involved in RNA metabolism as well as CDK1. Depletion of TIAR accelerates mitotic entry and leads to chromosomal instability in response to replication stress, in a manner that can be alleviated by the concomitant depletion of Cdc25B or inhibition of CDK1. Since TIAR retains CDK1 in GMGs and attenuates CDK1 activity, we propose that the assembly of GMGs may represent a so far unrecognized mechanism that contributes to the activation of the G2/M checkpoint in mammalian cells.

Highlights

Entry into mitosis is a tightly controlled process essential for faithful inheritance of the genome
We show that the RNAbinding protein TIAR is essential for the G2/M checkpoint and that TIAR accumulates in nuclear foci in late G2 and prophase in cells suffering from replication stress
Since TIAR retains CDK1 in G2/ M transition granules (GMGs) and attenuates CDK1 activity, we propose that the assembly of GMGs may represent a so far unrecognized mechanism that contributes to the activation of the G2/M checkpoint in mammalian cells

Summary

Introduction

Entry into mitosis is a tightly controlled process essential for faithful inheritance of the genome. The ataxia telangiectasia and Rad3-related protein kinase (ATR) acts as a guardian during the transition from S- to M-phase by ensuring that DNA is fully replicated before cells enter mitosis and partition their chromosomes [4]. If the ATR-Chk pathway cannot be activated in the presence of stalled replication forks, cells fail to resume DNA synthesis, which in turn causes the collapse of replication forks, the entry of unreplicated DNA into mitosis, and the formation of DNA doublestrand breaks (DSBs) [9,10]. ATR inhibitors do not cause cH2AX accumulation (as a marker of DSBs) in the absence of Cdc25A [11], demonstrating the essential role of controlling mitotic entry

Methods

Results

Conclusion