MSK1 functions as a transcriptional coactivator of p53 in the regulation of p21 gene expression

Jihye Ahn,Jaehoon Kim,Hee-Sung Park,Suna In,Jin Gyeong Lee,Chuevin Chin,Aerin Yang,Jeong Hyeon Park

doi:10.1038/s12276-018-0160-8

Abstract

Mitogen- and stress-activated kinase 1 (MSK1) is a chromatin kinase that facilitates activator-dependent transcription by altering chromatin structure through histone H3 phosphorylation. The kinase activity of MSK1 is activated by intramolecular autophosphorylation, which is initially triggered by the activation of upstream mitogen-activated protein kinases (MAPKs), such as p38 and ERK1/2. MSK1 has been implicated in the expression of p21, a p53 target gene; however, the precise connection between MSK1 and p53 has not been clearly elucidated. Here, using in vitro and cell-based transcription assays, we show that MSK1 functions as a transcriptional coactivator of p53 in p21 expression, an action associated with MAPK-dependent phosphorylation of MSK1 and elevated kinase activity. Of special significance, we show that MSK1 directly interacts with p53 and is recruited to the p21 promoter, where it phosphorylates histone H3 in a p53-dependent manner. In addition, phosphomimetic mutant analysis demonstrated that negative charges in the hydrophobic motif are critical for serine 212 phosphorylation in the N-terminal kinase domain, which renders MSK1 competent for histone kinase activity. These studies suggest that MSK1 acts through a direct interaction with p53 to function as a transcriptional coactivator and that MSK1 activation by upstream MAPK signaling is important for efficient p21 gene expression.

Highlights

Activation of mitogen-activated protein kinases (MAPKs) by multiple upstream kinase cascades transduces extracellular signals that regulate diverse cellular processes, including gene expression
Our study shows that Mitogen- and stress-activated kinase 1 (MSK1) serves as a transcriptional coactivator of the tumor suppressor p53 through direct interaction with p53, such that activation of the p38 MAPK pathway enhances its coactivator function, resulting in a greater transcriptional response of the p53 target gene p21
We demonstrate that p53-dependent phosphorylation of chromatin by MSK1 enhances p21 transcription, as evidenced by in vitro chromatin transcription as well as cell-based analyses

Summary

Introduction

Activation of mitogen-activated protein kinases (MAPKs) by multiple upstream kinase cascades transduces extracellular signals that regulate diverse cellular processes, including gene expression. MSK1/2 contain two independent kinase domains, an Nterminal kinase domain (NKD) and a C-terminal kinase domain (CKD), connected by a regulatory linker region. Two canonical MAPKs, p38 and ERK1/2, activate MSK1/ 2 by interacting with the MAPK-binding domain near the C-terminal nuclear localization sequence within MSK1/21,2. Mutagenesis studies of MSK1 suggest that upstream MAPKs phosphorylate three critical serine/threonine residues located in the linker region (serine 360), the activation loop of the CKD (threonine 581), and near a putative autoinhibitory domain (threonine 700)[4,5]. Activated CKD autophosphorylates the activation loop in NKD (serine 212) and the hydrophobic motif in the linker region (serine 376/381).

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Results

Conclusion