Characterization of a helicase-like transcription factor involved in the expression of the human plasminogen activator inhibitor-1 gene

A 5,4-kb cDNA encoding the protein that binds to the B Box of the plasminogen activator inhibitor-1 (PAI-1) gene was isolated and sequenced, The protein, named helicase-like transcription factor (HLTF), contains a DNA-binding domain, a RING finger domain, and seven helicase domains and is homologous to SWI/SNF proteins, Two HLTF mRNAs of 5.5 and 4.5 kb were detected in most human tissues, a single gene was located on chromosome 3q24-25, and the protein was located in the nucleoplasm. Two HLTF proteins differing in translation start site (Met-1 or Met-123) were obtained by in vitro translation in reticulocyte lysate or by immunoprecipitation from HeLa cell nuclear extracts, In vitro transcription from the PAI-1 promoter in HeLa cell extracts was inhibited by HLTF antibodies and by the HLTF DNA binding domain, Over-expression of HLTF or HLTFMet123 produced a three-fold induction of PAT-I-LUG transient expression in HeLa cells, Mutation of the PAT-I B Box led to an eight-fold reduction of basal PAT-I-LUG expression in these cell lines, but did not affect the four- to six-fold induction by phorbol esters.