Serum response factor MADS box serine -162 phosphorylation switches proliferation and myogenic gene programs

doi:10.1073/pnas.0505338103

Serum response factor MADS box serine -162 phosphorylation switches proliferation and myogenic gene programs

*Department of Medicine,
^†Division of Diabetes, Endocrinology, and Metabolism,
^‡Center for Cardiovascular Development, and Departments of
^§Molecular and Cellular Biology and
**Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, TX 77030;
^¶Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9148;
^‖Department of Medicine, University of Pennsylvania, Philadelphia, PA 19104; and
^‡‡Center for Molecular Development and Diseases, Institute of Biosciences and Technology, Texas A&M University System Health Science Center, Houston, TX 77030

Edited by Robert N. Eisenman, Fred Hutchinson Cancer Research Center, Seattle, WA, and approved December 2, 2005 (received for review July 1, 2005)

Abstract

Phosphorylation of a cluster of amino acids in the serum response factor (SRF) “MADS box” αI coil DNA binding domain regulated the transcription of genes associated with proliferation or terminal muscle differentiation. Mimicking phosphorylation of serine-162, a target of protein kinase C-α, with an aspartic acid substitution (SRF-S162D) completely inhibited SRF–DNA binding and blocked α-actin gene transcription even in the presence of potent myogenic cofactors, while preserving c-fos promoter activity because of stabilization of the ternary complex via Elk-1. Introduction of SRF-S162D into SRF null ES cells permitted transcription of the c-fos gene but was unable to rescue expression of myogenic contractile genes. Transition of proliferating C2C12 myoblasts to postfusion myocytes after serum withdrawal was associated with a progressive decline in SRF-S162 phosphorylation and an increase in α-actin gene expression. Hence, the phosphorylation status of serine-162 in the αI coil may constitute a novel switch that directs target gene expression into proliferation or differentiation programs.

Footnotes

^††To whom correspondence may be addressed. E-mail: ashokb{at}bcm.tmc.edu or rschwartz{at}ibt.tamhsc.edu
Author contributions: D.I., D.C., L.W., and R.J.S. designed research; D.I., D.C., J.M., L.W., and R.J.S. performed research; E.N.O. and M.S.P. contributed new reagents/analytic tools; D.I., E.N.O., A.B., and R.J.S. analyzed data; and A.B. and R.J.S. wrote the paper.
Conflict of interest statement: No conflicts declared.
This paper was submitted directly (Track II) to the PNAS office.
Abbreviations:

SRF,

serum response factor;

SRE,

serum response element;

SMA,

smooth muscle α-actin;

EBS,

Ets binding site;

MEK,

mitogen-activated protein kinase kinase;

Erk,

extracellular regulated kinase;

PMA,

phorbol 12-myristate 13-acetate;

HA,

hemagglutinin.