Interaction of Smads with collagen types I, III, and V.
Ontogenesis of the mammalian orofacial region is controlled by numerous developmental signals, including those initiated by the transforming growth factors beta (TGFbetas). Targeted deletion of the genes encoding several of the TGFbetas in mice has been shown to result in clefts of the secondary palate. Members of the TGFbeta family of growth factors utilize intracellular Smads as signal transducers. Smads 2 and 3 are transcriptional regulators that bind DNA through their conserved MH1 domains and activate/inhibit transcription of TGFbeta-responsive genes through their MH2 domains. Using a yeast two-hybrid screen of a cDNA expression library constructed from fetal murine orofacial tissue, we have identified three types of collagens (types I, III, and V) that are capable of binding to the MH2 domain of Smad 3. These interactions were confirmed by glutathione S-transferase (GST) pull-down assays in which the MH2 domain of Smad 3 fused to GST interacted strongly with in vitro translated, 35S-labeled collagen types I, III, and V. Each collagen also bound to the MH2 domains of Smads 4 and 7 and, to a lesser extent, full-length Smads 1, 2, 3, and 4. Binding of Smads to collagen is a novel observation. Moreover, TGFbeta is a potent regulator of collagen synthesis and turnover during mammalian orofacial development. These data thus suggest an important means of feedback regulation of the TGFbeta signaling cascade.
Ellis
Leslie R
LR
Department of Molecular, Cellular, and Craniofacial Biology, ULSD, University of Louisville Birth Defects Center, Louisville, KY 40292, USA.
Warner
Dennis R
DR
Greene
Robert M
RM
Pisano
M Michele
MM
D000818:Animals; D003094:Collagen / Q000145:classification / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005982:Glutathione Transferase / Q000378:metabolism; D051379:Mice; D008813:Mice, Inbred ICR; D011485:Protein Binding; D051785:Smad Proteins; D015534:Trans-Activators / Q000378:metabolism*; D014158:Transcription, Genetic / Q000502:physiology; D016212:Transforming Growth Factor beta / Q000502:physiology; D020798:Two-Hybrid System Techniques
D004268:DNA-Binding Proteins; D051785:Smad Proteins; D015534:Trans-Activators; D016212:Transforming Growth Factor beta; D003094:Collagen; D005982:Glutathione Transferase