| First Author | Shi X | Year | 1999 |
| Journal | J Biol Chem | Volume | 274 |
| Issue | 19 | Pages | 13711-7 |
| PubMed ID | 10224145 | Mgi Jnum | J:54898 |
| Mgi Id | MGI:1336572 | Doi | 10.1074/jbc.274.19.13711 |
| Citation | Shi X, et al. (1999) Smad1 interacts with homeobox DNA-binding proteins in bone morphogenetic protein signaling. J Biol Chem 274(19):13711-7 |
| abstractText | Bone morphogenetic proteins (BMP) transduce their signals into the cell through a family of mediator proteins known as Smads. Upon phosphorylation by the BMP receptors, Smad1 interacts with Smad4 and translocates into the nucleus where the complex recruits DNA-binding protein(s) to activate specific gene transcription. However, the DNA-binding protein(s) involved in BMP signaling has not been identified. Using a yeast two-hybrid approach, we found that Smad1 interacts with Hoxc-8, a homeodomain transcription factor. The interaction between Smad1 and Hoxc-8 was confirmed by a pull-down assay and a co-immunoprecipitation experiment in COS-1 cells. Interestingly, purified Smad1 inhibited Hoxc-8 binding to the osteopontin Hoxc-8 site in a concentration-dependent manner. Transient transfection studies showed that native osteopontin promoter activity was elevated upon BMP stimulation. Consistent with the gel shift assay, overexpression of Hoxc-8 abolished the BMP stimulation. When a wild type or mutant Hoxc-8 binding element was linked to an SV40 promoter-driven reporter gene, the wild type but not the mutant Hoxc-8 binding site responded to BMP stimulation. Again, overexpression of Hoxc-8 suppressed the BMP-induced activity of the wild type reporter construct. Our findings suggest that Smad1 interaction with Hoxc-8 dislodges Hoxc-8 from its DNA binding element, resulting in the induction of gene expression. |
