Control of MEF2 Transcriptional Activity by Coordinated Phosphorylation and Sumoylation

Serge Grégoire,Annie M Tremblay,Lin Xiao,Qian Yang,Kewei Ma,Jianyun Nie,Zixu Mao,Zhenguo Wu,Vincent Giguère,Xiang-Jiao Yang

doi:10.1074/jbc.m509471200

Abstract

A eukaryotic protein is often subject to regulation by multiple modifications like phosphorylation, acetylation, ubiquitination, and sumoylation. How these modifications are coordinated in vivo is an important issue that is poorly understood but is relevant to many biological processes. We recently showed that human MEF2D (myocyte enhancer factor 2D) is sumoylated on Lys-439. Adjacent to the sumoylation motif is Ser-444, which like Lys-439 is highly conserved among MEF2 proteins from diverse species. Here we present [corrected] several lines of evidence to demonstrate that Ser-444 of MEF2D is required for sumoylation of Lys-439. Histone deacetylase 4 (HDAC4) stimulated this modification by acting through Ser-444. In addition, phosphorylation of Ser-444 by Cdk5, a cyclin-dependent kinase known to inhibit MEF2 transcriptional activity, stimulated sumoylation. Opposing the actions of HDAC4 and Cdk5, calcineurin (also known as protein phosphatase 2B) dephosphorylated Ser-444 and inhibited sumoylation of Lys-439. This phosphatase, however, exerted minimal effects on the phosphorylation catalyzed by ERK5, an extracellular signal-regulated kinase known to activate MEF2D. These results identify [corrected] an essential role for Ser-444 in MEF2D sumoylation and reveal [corrected] a novel mechanism by which calcineurin selectively "edits" phosphorylation at different sites, thereby reiterating that interplay between different modifications represents a general mechanism for coordinated regulation of eukaryotic protein functions in vivo.

Highlights

Some of them were subsequently shown to be important for cardiac myogenesis; null mutation of the murine MEF2A or MEF2C gene led to cardiac death [3,4,5], and a mutation on the human MEF2A gene was recently suggested to play a role in coronary artery disease [6]
Histone deacetylase 4 (HDAC4) stimulated this modification, and roscovitine inhibited the stimulation. This inhibitor had minimal effects on the migration shifts of MEF2D (Fig. 2G, lane 3, bottom), supporting the involvement of additional phosphorylation events. These results suggest that HDAC4 recruits cyclin-dependent kinase 5 (Cdk5) to phosphorylate Ser-444 and promote Lys-439 sumoylation
It was reported that a novel Liϩ-sensitive kinase phosphorylates MEF2D [56]. These results suggest that HDAC4 recruits Cdk5, as well as an unknown Liϩ-sensitive kinase, to phosphorylate MEF2D and stimulate sumoylation

Summary

Introduction

Cyclin-dependent kinase 5 (Cdk5) phosphorylates Ser-444 of human MEF2D and reduces its transcriptional potential during neurotoxicity-induced apoptosis [17, 42]. Just four residues away from Ser-444 is Lys-439, whose sumoylation serves as an inhibitory mechanism [32, 43] Both residues are highly conserved among different MEF2 proteins and form a portable repression domain [17, 19, 32]. We conclude that phosphorylation of Ser-444 interplays with sumoylation of Lys-439 to regulate transcriptional and myogenic activities of MEF2 in a coordinated fashion

Results

Discussion

Conclusion