Smad proteins function as co-modulators for MEF2 transcriptional regulatory proteins

• Published in: Nucleic acids research 2001-02, Vol.29 (3), p.732-742
• Main Authors: Quinn, Z A, Yang, C C, Wrana, J L, McDermott, J C
• Format: Article
• Language: English
• Subjects: Animals; Binding Sites; Cell Line; Cell Nucleus - metabolism; COS Cells; Cytoplasm - metabolism; DNA, Recombinant; DNA-Binding Proteins - genetics; DNA-Binding Proteins - metabolism; DNA-Binding Proteins - physiology; MEF2 Transcription Factors; Mitogen-Activated Protein Kinases - metabolism; Myogenic Regulatory Factors - genetics; Myogenic Regulatory Factors - metabolism; p38 Mitogen-Activated Protein Kinases; Phosphorylation; Plasmids - genetics; Protein Binding; Receptors, Transforming Growth Factor beta - genetics; Receptors, Transforming Growth Factor beta - physiology; Smad2 Protein; Trans-Activators - genetics; Trans-Activators - metabolism; Trans-Activators - physiology; Transcription Factors - genetics; Transcription Factors - metabolism; Transcriptional Activation - drug effects; Transfection; Transforming Growth Factor beta - pharmacology
• ISSN: 1362-4962; 0305-1048; 1362-4962
• DOI: 10.1093/nar/29.3.732

An emerging theme in transforming growth factor-ss (TGF-ss) signalling is the association of the Smad proteins with diverse groups of transcriptional regulatory proteins. Several Smad cofactors have been identified to date but the diversity of TGF-ss effects on gene transcription suggests that interactions with other co-regulators must occur. In these studies we addressed the possible interaction of Smad proteins with the myocyte enhancer-binding factor 2 (MEF2) transcriptional regulators. Our studies indicate that Smad2 and 4 (Smad2/4) complexes cooperate with MEF2 regulatory proteins in a GAL4-based one-hybrid reporter gene assay. We have also observed in vivo interactions between Smad2 and MEF2A using co-immunoprecipitation assays. This interaction is confirmed by glutathione S:-transferase pull-down analysis. Immunofluorescence studies in C2C12 myotubes show that Smad2 and MEF2A co-localise in the nucleus of multinuclear myotubes during differentiation. Interestingly, phospho-acceptor site mutations of MEF2 that render it unresponsive to p38 MAP kinase signalling abrogate the cooperativity with the Smads suggesting that p38 MAP Kinase-catalysed phosphorylation of MEF2 is a prerequisite for the Smad-MEF2 interaction. Thus, the association between Smad2 and MEF2A may subserve a physical link between TGF-ss signalling and a diverse array of genes controlled by the MEF2 cis element.