ERK phosphorylation of MED14 in promoter complexes during mitogen-induced gene activation by Elk-1.
The ETS domain transcription factor Elk-1 stimulates expression of immediate early genes (IEGs) in response to mitogens. These events require phosphorylation of Elk-1 by extracellular signal-regulated kinase (ERK) and phosphorylation-dependent interaction of Elk-1 with co-activators, including histone acetyltransferases and the Mediator complex. Elk-1 also recruits ERK to the promoters of its target genes, suggesting that ERK phosphorylates additional substrates in transcription complexes at mitogen-responsive promoters. Here we report that MED14, a core subunit of the Mediator, is a bona fide ERK substrate and identify serine 986 (S986) within a serine-proline rich region of MED14 as the major ERK phosphorylation site. Mitogens induced phosphorylation of MED14 on S986 at IEG promoters; RNAi knockdown of MED14 reduced CDK8 and RNA polymerase II (RNAPII) recruitment, RNAPII C-terminal domain phosphorylation and impaired activation of IEG transcription. A single alanine substitution at S986 reduced activation of an E26 (ETS)-responsive reporter by oncogenic Ras and mitogen-induced, Elk-1-dependent transcription, whereas activities of other transcriptional activators were unaffected. We also demonstrate that Elk-1 can associate with MED14 independently of MED23, which may facilitate phosphorylation of MED14 by ERK to impart a positive and selective impact on mitogen-responsive gene expression.
School of Biomedical Sciences, University of Nottingham, Queen's Medical Centre, Nottingham, NG7 2UH, UK, Department of Molecular, Cellular and Developmental Biology, Howard Hughes Medical Institute, University of Colorado at Boulder, Boulder, CO 80309, USA, Department of Neurology, Center of Regeneration Medicine and Stem Cell Research, University of California, San Francisco, CA 90089, USA and Department of Pharmacology, Ningxia Medical University, Yinchuan 750004, China.
Matthew D
MD
Galbraith
Janice
J
Saxton
Li
L
Li
Samuel J
SJ
Shelton
Hongmei
H
Zhang
Joaquin M
JM
Espinosa
Peter E
PE
Shaw
D000818:Animals; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D017781:Genes, Immediate-Early; D011905:Genes, ras; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D056892:Mediator Complex / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008934:Mitogens / Q000494:pharmacology*; D009154:Mutation; D041681:NIH 3T3 Cells; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D015533:Transcriptional Activation; D050807:ets-Domain Protein Elk-1 / Q000378:metabolism*
C492160:MED14 protein, human; D056892:Mediator Complex; D008934:Mitogens; D050807:ets-Domain Protein Elk-1; D048049:Extracellular Signal-Regulated MAP Kinases