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 plas minogen activator inhibitor-1 (PAI-1) gene was isolated and sequenced, The protein, named helicase-like transcription factor (HLTF), contain s a DNA-binding domain, a RING finger domain, and seven helicase domai ns 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. T wo HLTF proteins differing in translation start site (Met-1 or Met-123 ) were obtained by in vitro translation in reticulocyte lysate or by i mmunoprecipitation from HeLa cell nuclear extracts, In vitro transcrip tion from the PAI-1 promoter in HeLa cell extracts was inhibited by HL TF antibodies and by the HLTF DNA binding domain, Over-expression of H LTF or HLTFMet123 produced a three-fold induction of PAT-I-LUG transie nt expression in HeLa cells, Mutation of the PAT-I B Box led to an eig ht-fold reduction of basal PAT-I-LUG expression in these cell lines, b ut did not affect the four- to six-fold induction by phorbol esters.