Differentiation-dependent association of phosphorylated extracellular signal-regulated kinase with the chromatin of osteoblast-related genes.
The ERK/MAP kinase pathway is an important regulator of gene expression and differentiation in postmitotic cells. To understand how this pathway controls gene expression in bone, we examined the subnuclear localization of P-ERK in differentiating osteoblasts. Induction of differentiation was accompanied by increased ERK phosphorylation and expression of osteoblast-related genes, including osteocalcin (Bglap2) and bone sialoprotein (Ibsp). Confocal immunofluorescence microscopy revealed that P-ERK colocalized with the RUNX2 transcription factor in the nuclei of differentiating cells. Interestingly, a portion of this nuclear P-ERK was directly bound to the proximal promoter regions of Bglap2 and Ibsp. Furthermore, the level of P-ERK binding to chromatin increased with differentiation, whereas RUNX2 binding remained relatively constant. The P-ERK-chromatin interaction was seen only in RUNX2-positive cells, required intact RUNX2-selective enhancer sequences, and was blocked with MAPK inhibition. These studies show for the first time that RUNX2 specifically targets P-ERK to the chromatin of osteoblast-related genes, where it may phosphorylate multiple substrates, including RUNX2, resulting in altered chromatin structure and gene expression.
Li
Yan
Y
Department of Periodontics and Oral Medicine, University of Michigan School of Dentistry, Ann Arbor, MI 48109, USA.
Ge
Chunxi
C
Franceschi
Renny T
RT
D000818:Animals; D002454:Cell Differentiation / Q000235:genetics*; D002467:Cell Nucleus / Q000201:enzymology; D002843:Chromatin / Q000378:metabolism*; D050659:Core Binding Factor Alpha 1 Subunit / Q000378:metabolism; D004789:Enzyme Activation; D005109:Extracellular Matrix / Q000378:metabolism; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D005786:Gene Expression Regulation; D058574:Integrin-Binding Sialoprotein; D020935:MAP Kinase Signaling System; D051379:Mice; D010006:Osteoblasts / Q000166:cytology* / Q000378:metabolism*; D015675:Osteocalcin / Q000235:genetics; D010766:Phosphorylation; D011485:Protein Binding; D021381:Protein Transport; D012045:Regulatory Sequences, Nucleic Acid / Q000235:genetics; D012795:Sialoglycoproteins / Q000235:genetics; D013997:Time Factors
D002843:Chromatin; D050659:Core Binding Factor Alpha 1 Subunit; C546872:Ibsp protein, mouse; D058574:Integrin-Binding Sialoprotein; D012795:Sialoglycoproteins; D015675:Osteocalcin; D048049:Extracellular Signal-Regulated MAP Kinases