Functional interactions between Sp1 or Sp3 and the helicase-like transcription factor mediate basal expression from the human plasminogen activator inhibitor-1 gene.

Basal expression of the human plasminogen activator inhibitor-1 (PAI-1) is mediated by a promoter element named B box that binds the helicase-like transcription factor (HLTF), homologous to SNF/SWI proteins. Electrophoretic mobility shift assays performed on a set of B box point mutants demonstrated two HLTF sites flanking and partially overlapping ...
with a GT box binding Sp1 and Sp3. Mutations affecting either the Sp1/Sp3 or the two HLTF sites inhibited by 6- and 2.5-fold, respectively, transient expression in HeLa cells of a reporter gene fused to the PAI-1 promoter. In Sp1/Sp3-devoid insect cells, co-expression of PAI-1-lacZ with Sp1 or Sp3 led to a 14-26-fold induction while HLTF had no effect. Simultaneous presence of Sp1 or Sp3 and the short HLTF form (initiating at Met-123) provided an additional 2-3-fold synergistic activation suppressed by mutations that prevented HLTF binding. Moreover, a DNA-independent interaction between HLTFMet123 and Sp1/Sp3 was demonstrated by co-immunoprecipitation from HeLa cell extracts and glutathione S-transferase pull-down experiments. The interaction domains were mapped to the carboxyl-terminal region of each protein; deletion of the last 85 amino acids of HLTFMet123 abolished the synergy with Sp1. This is the first demonstration of a functional interaction between proteins of the Sp1 and SNF/SWI families.
Mesh Terms:
Binding Sites, DNA-Binding Proteins, Gene Expression Regulation, Genes, Reporter, HeLa Cells, Humans, Mutagenesis, Plasminogen Activator Inhibitor 1, Promoter Regions, Genetic, Recombinant Proteins, Sp1 Transcription Factor, Sp3 Transcription Factor, Transcription Factors, Transcription, Genetic, Transfection
J. Biol. Chem.
Date: Jul. 09, 1999
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