Novel phosphorylation target in the serum response factor MADS box regulates alpha-actin transcription.
Serum response factor (SRF) is a phosphoprotein that regulates skeletal and cardiac alpha-actin gene transcription. Myotonic dystrophy protein kinase (DMPK), a muscle- and neuron-restricted kinase, enhanced SRF-mediated promoter activity of the skeletal and cardiac alpha-actin genes in C2C12 myoblasts as well as in nonmyogenic cells. DMPK phosphorylated SRF in vitro in the alphaI coil of the DNA-binding domain in the MADS box, a highly conserved region required for DNA binding, dimerization, and co-activator interaction in COS and CV1 cells. Threonine 159 in the MADS box alphaI coil was a specific phosphorylation target in vitro as well as in vivo of both DMPK and protein kinase C-alpha. Substitution of threonine 159 with the nonphosphorylatable residue alanine markedly diminished activation of the cardiac alpha-actin promoter in the presence of kinase, while its substitution with aspartic acid, to introduce a negative charge and mimic phosphorylation, restored activation completely. Phosphorylation of the MADS box may constitute a novel mechanism for regulation of SRF-dependent actin gene transcription.
Iyer
Dinakar
D
Department of Medicine, Division of Endocrinology, Baylor College of Medicine, Houston, Texas 77030, USA.
Belaguli
Narasimhaswamy
N
Flück
Martin
M
Rowan
Brian G
BG
Wei
Lei
L
Weigel
Nancy L
NL
Booth
Frank W
FW
Epstein
Henry F
HF
Schwartz
Robert J
RJ
Balasubramanyam
Ashok
A
D000199:Actins / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism*; D019943:Amino Acid Substitution; D000818:Animals; D000906:Antibodies / Q000032:analysis / Q000737:chemistry / Q000276:immunology; D019556:COS Cells; D002460:Cell Line; D002522:Chlorocebus aethiops; D008156:Luciferases / Q000235:genetics; D018482:Muscle, Skeletal / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism; D065636:Myotonin-Protein Kinase; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D011493:Protein Kinase C / Q000235:genetics / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D026362:Serum Response Factor / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D013912:Threonine / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic / Q000502:physiology; D014162:Transfection
D000199:Actins; D000906:Antibodies; D011994:Recombinant Proteins; D026362:Serum Response Factor; D013912:Threonine; D008156:Luciferases; D065636:Myotonin-Protein Kinase; D017346:Protein Serine-Threonine Kinases; D011493:Protein Kinase C