Both Max and TFE3 cooperate with Smad proteins to bind the plasminogen activator inhibitor-1 promoter, but they have opposite effects on transcriptional activity.
Transforming growth factor (TGF)-beta regulates gene expression in large part through combinatorial interactions between members of the Smad family and other transcription factors. The basic helix-loop-helix leucine zipper (bHLHZIP) protein TFE3 and Smad3 synergistically activate transcription of the plasminogen activator inhibitor-1 (PAI-1) as well as other genes. We investigated interactions among different bHLHZIP and Smad family proteins. TFE3, TFEB, and Max associated with Smad3 and Smad4 in the absence of DNA and at the PE2.1 element of the PAI-1 promoter. These interactions were mediated by the leucine zipper and MH1 regions of the respective proteins. No interactions were observed with the E47 bHLH family protein. Chimeric proteins, in which leucine zippers from bHLHZIP or bZIP proteins were fused to heterologous bHLH domains, associated with Smad proteins both in the absence of DNA and at the PE2.1 element. The kinetics of bHLHZIP and Smad protein binding at the PE2.1 element were examined using surface plasmon resonance analysis. TFE3 exhibited cooperative DNA binding with Smad proteins, whereas no cooperativity was observed between E47 and Smads. Max inhibited transcription activation by Smad3 and TGF-beta at the PAI-1 promoter, whereas TFE3 and TFEB stimulated transcription activation. These results suggest that Smad family proteins can interact with several bHLHZIP proteins, resulting in different transcriptional outcomes.
Grinberg
Asya V
AV
Howard Hughes Medical Institute and Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan 48109, USA.
Kerppola
Tom
T
D001483:Base Sequence; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D050976:Basic-Leucine Zipper Transcription Factors; D004268:DNA-Binding Proteins / Q000378:metabolism* / Q000502:physiology; D024202:Electrophoretic Mobility Shift Assay; D006801:Humans; D016350:Leucine Zippers; D009841:Oligonucleotides; D017395:Plasminogen Activator Inhibitor 1 / Q000235:genetics*; D011401:Promoter Regions, Genetic; D012689:Sequence Homology, Nucleic Acid; D051900:Smad3 Protein; D020349:Surface Plasmon Resonance; D015534:Trans-Activators / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism* / Q000502:physiology; D014158:Transcription, Genetic / Q000502:physiology*
D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D050976:Basic-Leucine Zipper Transcription Factors; D004268:DNA-Binding Proteins; C499330:MAX protein, human; C067850:Myc associated factor X; D009841:Oligonucleotides; D017395:Plasminogen Activator Inhibitor 1; C497790:SMAD3 protein, human; D051900:Smad3 Protein; C069203:TFE3 protein, human; D015534:Trans-Activators; D014157:Transcription Factors