TGFbeta and BMP-2 activation of the OPN promoter: roles of smad- and hox-binding elements.
Members of the transforming growth factor superfamily are known to transduce signals via the activation of Smad proteins. Ligand binding to transmembrane cell surface receptors triggers the phosphorylation of pathway-specific Smads. These Smads then complex with Smad 4 and are translocated to the nucleus where they effect gene transcription. Smads 1 and 4 were recently demonstrated to mediate BMP activation of the OPN promoter by inhibiting the interaction of Hoxc-8 protein with a Hox-binding element. While previous studies have indicated that specific DNA sequences are recognized by Smad complexes in several promoters, the role of Smad-binding elements (SBEs) in activation of the OPN promoter by members of the TGFbeta superfamily has not been previously evaluated. In this study we tested the hypothesis that a putative Smad-binding region containing the sequence AGACTGTCTGGAC is involved in the activation of the OPN promoter by members of the TGFbeta superfamily. Functional analyses demonstrated that the both the HBE- and Smad-binding region were involved in BMP-2-induced activation of the promoter, whereas, the HBE appeared to be the primary region involved in activation by TGFbeta. Deletion of the first 9 bases in the Smad-binding region substantially reduced BMP-2-mediated activation of the promoter. These results strongly suggest that both the Hox- and the Smad-binding regions play a role in BMP-2-induced activation of the OPN promoter.
Hullinger
T G
TG
Cardiovascular Therapeutics, Pfizer Inc., Ann Arbor, Michigan, 48105, USA.
Pan
Q
Q
Viswanathan
H L
HL
Somerman
M J
MJ
D016475:3T3 Cells; D000818:Animals; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D018398:Homeodomain Proteins / Q000378:metabolism*; D051379:Mice; D053495:Osteopontin; D011401:Promoter Regions, Genetic; D012045:Regulatory Sequences, Nucleic Acid; D012795:Sialoglycoproteins / Q000235:genetics*; D051785:Smad Proteins; D051901:Smad4 Protein; D015534:Trans-Activators / Q000378:metabolism*; D015533:Transcriptional Activation; D016212:Transforming Growth Factor beta / Q000378:metabolism*
C525719:Bmp2 protein, mouse; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins; D004268:DNA-Binding Proteins; C489815:HOXC8 protein, human; D018398:Homeodomain Proteins; C489816:Hoxc8 protein, mouse; C506895:SPP1 protein, human; D012795:Sialoglycoproteins; D051785:Smad Proteins; D051901:Smad4 Protein; C490810:Smad4 protein, mouse; C506896:Spp1 protein, mouse; D015534:Trans-Activators; D016212:Transforming Growth Factor beta; D053495:Osteopontin