AP1 binding site is another target of FGF2 regulation of bone sialoprotein gene transcription.
Bone sialoprotein (BSP) is an early marker of osteoblast differentiation. We previously reported that fibroblast growth factor 2 (FGF2) regulates BSP gene transcription via FGF2 response element (FRE) in the proximal promoter of rat BSP gene. We here report that activator protein 1 (AP1) binding site overlapping with glucocorticoid response element (GRE) AP1/GRE in the rat BSP gene promoter is another target of FGF2. Using the osteoblastic cell line ROS17/2.8, we determined that BSP mRNA levels increased by 10 ng/ml FGF2 at 6 and 12 h. Runx2 protein levels increased by FGF2 (10 ng/ml) at 3 h. Treatment of ROS17/2.8 cells with FGF2 (10 ng/ml, 12 h) increased luciferase activities of constructs including -116 to +60 and -938 to +60 of the rat BSP gene promoter. Effects of FGF2 abrogated in constructs included 2 bp mutations in the FRE and AP1/GRE elements. Luciferase activities induced by FGF2 were blocked by tyrosine kinase inhibitor herbimycin A, src-tyrosine kinase inhibitor PP1 and MAP kinase kinase inhibitor U0126. Gel shift analyses showed that FGF2 increased binding of FRE and AP1/GRE elements. Notably, the AP1/GRE-protein complexes were supershifted by Smad1 and c-Fos antibodies, c-Jun and Dlx5 antibodies disrupted the complexes formation, on the other hand AP1/GRE-protein complexes did not change by Runx2 antibody. These studies demonstrate that FGF2 stimulates BSP gene transcription by targeting the FRE and AP1/GRE elements in the rat BSP gene promoter.
Takai
Hideki
H
Department of Periodontology, Nihon University School of Dentistry at Matsudo, Chiba, Japan.
Araki
Shouta
S
Mezawa
Masaru
M
Kim
Dong-Soon
DS
Li
Xinyue
X
Yang
Li
L
Li
Zhengyang
Z
Wang
Zhitao
Z
Nakayama
Youhei
Y
Ogata
Yorimasa
Y
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D001842:Bone and Bones / Q000378:metabolism*; D050659:Core Binding Factor Alpha 1 Subunit / Q000378:metabolism; D017931:DNA Primers; D016222:Fibroblast Growth Factor 2 / Q000502:physiology*; D005786:Gene Expression Regulation / Q000502:physiology*; D058574:Integrin-Binding Sialoprotein; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D012795:Sialoglycoproteins / Q000235:genetics*; D018808:Transcription Factor AP-1 / Q000378:metabolism*; D014158:Transcription, Genetic / Q000502:physiology*
D050659:Core Binding Factor Alpha 1 Subunit; D017931:DNA Primers; C546873:Ibsp protein, rat; D058574:Integrin-Binding Sialoprotein; D012333:RNA, Messenger; C493717:Runx2 protein, rat; D012795:Sialoglycoproteins; D018808:Transcription Factor AP-1; D016222:Fibroblast Growth Factor 2