BMP2-activated Erk/MAP kinase stabilizes Runx2 by increasing p300 levels and histone acetyltransferase activity.
Runx2 is a critical transcription factor for osteoblast differentiation. Regulation of Runx2 expression levels and transcriptional activity is important for bone morphogenetic protein (BMP)-induced osteoblast differentiation. Previous studies have shown that extracellular signal-regulated kinase (Erk) activation enhances the transcriptional activity of Runx2 and that BMP-induced Runx2 acetylation increases Runx2 stability and transcriptional activity. Because BMP signaling induces Erk activation in osteoblasts, we sought to investigate whether BMP-induced Erk signaling regulates Runx2 acetylation and stability. Erk activation by overexpression of constitutively active MEK1 increased Runx2 transcriptional activity, whereas U0126, an inhibitor of MEK1/2, suppressed basal Runx2 transcriptional activity and BMP-induced Runx2 acetylation and stabilization. Overexpression of constitutively active MEK1 stabilized Runx2 protein via up-regulation of acetylation and down-regulation of ubiquitination. Erk activation increased p300 protein levels and histone acetyltransferase activity. Knockdown of p300 using siRNA diminished Erk-induced Runx2 stabilization. Overexpression of Smad5 increased Runx2 acetylation and stabilization. Erk activation further increased Smad-induced Runx2 acetylation and stabilization, whereas U0126 suppressed these functions. On the other hand, knockdown of Smad1 and Smad5 by siRNA suppressed both basal and Erk-induced Runx2 protein levels. Erk activation enhanced the association of Runx2 with p300 and Smad1. Taken together these results indicate that Erk signaling increases Runx2 stability and transcriptional activity, partly via increasing p300 protein levels and histone acetyltransferase activity and subsequently increasing Runx2 acetylation by p300. In addition to the canonical Smad pathway, a BMP-induced non-Smad Erk signaling pathway cooperatively regulates osteoblast differentiation partly via increasing the stability and transcriptional activity of Runx2.
Jun
Ji Hae
JH
Department of Molecular Genetics, School of Dentistry and Dental Research Institute, BK21 Program, Seoul National University, Seoul 110-749, Republic of Korea.
Yoon
Won-Joon
WJ
Seo
Sang-Beom
SB
Woo
Kyung-Mi
KM
Kim
Gwan-Shik
GS
Ryoo
Hyun-Mo
HM
Baek
Jeong-Hwa
JH
D000107:Acetylation; D000818:Animals; D015153:Blotting, Western; D055396:Bone Morphogenetic Protein 2 / Q000235:genetics / Q000378:metabolism*; D002454:Cell Differentiation; D002478:Cells, Cultured; D050659:Core Binding Factor Alpha 1 Subunit / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D050881:E1A-Associated p300 Protein / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000235:genetics / Q000378:metabolism*; D051548:Histone Acetyltransferases / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D047468:Immunoprecipitation; D008156:Luciferases / Q000378:metabolism; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed; D032446:Myoblasts / Q000166:cytology / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D051785:Smad Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D015533:Transcriptional Activation; D054875:Ubiquitination; D015854:Up-Regulation
C525718:BMP2 protein, human; D055396:Bone Morphogenetic Protein 2; D050659:Core Binding Factor Alpha 1 Subunit; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D051785:Smad Proteins; D008156:Luciferases; D050881:E1A-Associated p300 Protein; C494360:EP300 protein, human; D051548:Histone Acetyltransferases; D048049:Extracellular Signal-Regulated MAP Kinases; D020928:Mitogen-Activated Protein Kinases