Insulin-like growth factor-II regulates bone sialoprotein gene transcription

Odontology. 2016 Sep;104(3):271-81. doi: 10.1007/s10266-015-0205-6. Epub 2015 Apr 21.


Insulin-like growth factor-I and -II (IGF-I and IGF-II) have been found in bone extracts of several different species, and IGF-II is the most abundant growth factor stored in bone. Bone sialoprotein (BSP) is a noncollagenous extracellular matrix glycoprotein associated with mineralized connective tissues. In this study, we have investigated the regulation of BSP transcription by IGF-II in rat osteoblast-like ROS17/2.8 cells. IGF-II (50 ng/ml) increased BSP mRNA and protein levels after 6-h stimulation, and enhanced luciferase activities of the constructs pLUC3 (-116 to +60), pLUC4 (-425 to +60), pLUC5 (-801 to +60) and pLUC6 (-938 to +60). Effects of IGF-II were inhibited by tyrosine kinase, extracellular signal-regulated kinase1/2 and phosphatidylinositol 3-kinase inhibitors, and abrogated by 2-bp mutations in cAMP response element (CRE), FGF2 response element (FRE) and homeodomain protein-binding site (HOX). The results of gel shift assays showed that nuclear proteins binding to CRE, FRE and HOX sites were increased by IGF-II (50 ng/ml) at 3 and 6 h. CREB1, phospho-CREB1, c-Fos and c-Jun antibodies disrupted the formation of the CRE-protein complexes. Dlx5 and Runx2 antibodies disrupted the FRE- and HOX-protein complex formations. These studies therefore demonstrated that IGF-II increased BSP transcription by targeting CRE, FRE and HOX elements in the proximal promoter of the rat BSP gene. Moreover, phospho-CREB1, c-Fos, c-Jun, Dlx5 and Runx2 transcription factors appear to be key regulators of IGF-II effects on BSP transcription.

Keywords: Bone formation; Bone sialoprotein; IGF-II; Osteoblasts; Transcription.

MeSH terms

  • Animals
  • Cyclic AMP Response Element-Binding Protein / genetics
  • Fibroblast Growth Factor 2 / genetics
  • Homeodomain Proteins / genetics
  • Insulin-Like Growth Factor II / physiology*
  • Integrin-Binding Sialoprotein / genetics*
  • Mutation
  • Osteoblasts / metabolism*
  • Phosphoinositide-3 Kinase Inhibitors
  • Protein-Tyrosine Kinases / pharmacology
  • RNA, Messenger / analysis
  • Rats
  • Transcription Factors / physiology
  • Transcription, Genetic*


  • Cyclic AMP Response Element-Binding Protein
  • Homeodomain Proteins
  • Integrin-Binding Sialoprotein
  • Phosphoinositide-3 Kinase Inhibitors
  • RNA, Messenger
  • Transcription Factors
  • Fibroblast Growth Factor 2
  • Insulin-Like Growth Factor II
  • Protein-Tyrosine Kinases