Regulation of plasminogen activator inhibitor-1 expression by transforming growth factor-beta -induced physical and functional interactions between smads and Sp1.
Members of the transforming growth factor-beta (TGF-beta) superfamily mediate a broad range of biological activities by regulating the expression of target genes. Smad proteins play a critical role in this process by binding directly to the promoter elements and/or associating with other transcription factors. TGF-beta1 up-regulates several genes transcriptionally through Sp1 binding sites; however, the mechanism of TGF-beta induction of gene expression through Sp1 sites is largely unknown. Here we report the identification of a novel 38-base pair TGF-beta-responsive element in the human plasminogen activator inhibitor-1 (PAI-1) promoter, which contains two Sp1 binding sites, and is required for TGF-beta-induced Smad-dependent transcriptional activation. Three canonical Sp1 binding sites also support strong transcriptional activation by TGF-beta and Smads from a minimal heterologous promoter. TGF-beta induction of PAI-1 and p21 is blocked by the Sp1 inhibitor mithramycin, implicating Sp1 in the in vivo regulation of these genes by TGF-beta. We show that the association between endogenous Sp1 and Smad3 is induced by TGF-beta in several cell lines; however, Smad4 shows constitutive interaction with Sp1. These data provide novel insights into the mechanism by which TGF-beta up-regulates several gene expression by activating Sp1-dependent transcription through the induction of Smad/Sp1 complex formation.
Datta
P K
PK
Vanderbilt-Ingram Cancer Center, Departments of Cell Biology and Surgery, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA.
Blake
M C
MC
Moses
H L
HL
D000818:Animals; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000502:physiology*; D006801:Humans; D017395:Plasminogen Activator Inhibitor 1 / Q000096:biosynthesis / Q000235:genetics*; D051900:Smad3 Protein; D051901:Smad4 Protein; D016329:Sp1 Transcription Factor / Q000378:metabolism*; D015534:Trans-Activators / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000502:physiology*
D004268:DNA-Binding Proteins; D017395:Plasminogen Activator Inhibitor 1; C497790:SMAD3 protein, human; C497796:SMAD4 protein, human; D051900:Smad3 Protein; D051901:Smad4 Protein; D016329:Sp1 Transcription Factor; D015534:Trans-Activators; D016212:Transforming Growth Factor beta