Ribosomal S6 Kinase 2 (RSK2) Maintains Genomic Stability by Activating the Atm/p53-Dependent DNA Damage Pathway

Han Chi Lim,Zhong-Can Chen,Rong Li,Eng King Tan,Li Zeng,Li Xie,Wei Zhang,Guang-Zhi Wu,Shu-Sen Cui

doi:10.1371/journal.pone.0074334

Abstract

Ribosomal S6 Kinase 2 (RSK2) is a member of the p90RSK family of serine/threonine kinases, which are widely expressed and respond to many growth factors, peptide hormones, and neurotransmitters. Loss-of function mutations in the RPS6KA3 gene, which encodes the RSK2 protein, have been implicated in Coffin-Lowry Syndrome (CLS), an X-linked mental retardation disorder associated with cognitive deficits and behavioral impairments. However, the cellular and molecular mechanisms underlying this neurological disorder are not known. Recent evidence suggests that defective DNA damage signaling might be associated with neurological disorders, but the role of RSK2 in the DNA damage pathway remains to be elucidated. Here, we show that Adriamycin-induced DNA damage leads to the phosphorylation of RSK2 at Ser227 and Thr577 in the chromatin fraction, promotes RSK2 nuclear translocation, and enhances RSK2 and Atm interactions in the nuclear fraction. Furthermore, using RSK2 knockout mouse fibroblasts and RSK2-deficient cells from CLS patients, we demonstrate that ablation of RSK2 impairs the phosphorylation of Atm at Ser1981 and the phosphorylation of p53 at Ser18 (mouse) or Ser15 (human) in response to genotoxic stress. We also show that RSK2 affects p53-mediated downstream cellular events in response to DNA damage, that RSK2 knockout relieves cell cycle arrest at the G2/M phase, and that an increased number of γH2AX foci, which are associated with defects in DNA repair, are present in RSK2-deficient cells. Taken together, our findings demonstrated that RSK2 plays an important role in the DNA damage pathway that maintains genomic stability by mediating cell cycle progression and DNA repair.

Highlights

Coffin-Lowry syndrome (CLS) is an X-linked mental retardation disorder caused by mutations in the Rps6ka3 gene, which encodes ribosomal S6 kinase (RSK) 2 [1]
We found that after 2 hr of AD treatment, Ribosomal S6 Kinase 2 (RSK2) was phosphorylated at Ser227 (,1.6-fold) in the N-terminal kinase domain (NTKD) and Thr577 (,1.6-fold) in the Cterminal kinase domain (CTKD)
We found that while AD treatment of wild type (WT) cells leads to an induction of p21, a potent cyclindependent kinase inhibitor (CDKI) that functions as a regulator of cell cycle progression at the G1 phase [22], this effect was abolished in RSK2 KO cells (Fig. 2A)

Summary

Introduction

Coffin-Lowry syndrome (CLS) is an X-linked mental retardation disorder caused by mutations in the Rps6ka gene, which encodes ribosomal S6 kinase (RSK) 2 [1]. This syndrome is characterized by psychomotor, growth, and cognitive retardation, as well as facial, hand, and skeletal anomalies [2]. Loss of RSK2 function decreases neurogenesis during cerebral cortex development [6]. These data suggest that RSK2 plays an important role in learning and memory in both humans and mice and that RSK2 deficiency might lead to cognitive and behavioral dysfunction

Methods

Results

Conclusion