Myb and Ets related transcription factors are required for activity of the human lck type I promoter.
The lck gene, which encodes a lymphoid-specific Src family tyrosine kinase, is transcribed from two promoters that are differentially utilized during T cell development. We have shown previously that the human lck type I promoter, which is preferentially expressed in immature thymocytes, requires a binding site (-97 to -90) for the Ets family of transcription factors for its activity in Jurkat T leukemia cells. Three putative Myb binding sites (-86 to -82, -77 to -72 and -59 to -54) were analysed for their ability to activate the lck type I promoter. In vitro assays demonstrated specific binding of purified, bacterially expressed c-Myb DNA binding domain to the Myb (-59 to -54) site. Transient transfection assays using the site-directed mutants of the lck type I promoter in Jurkat cells revealed that mutation of the Myb (-59 to -54) site abolished transcriptional activity. In transiently transfected HeLa cells, the lck type I promoter was activated by co-transfection with a vector that expresses c-Myb. This c-Myb dependent activation required the presence of intact Myb and Ets binding sites, indicating that the expressed c-Myb functions with endogenous Ets related transcription factors to activate the lck type I promoter. This effect was further enhanced by co-transfection with vectors that express either Ets1 or Ets2. These results demonstrate that Myb and Ets related transcription factors synergistically activate the human lck type I promoter.
Division of Cellular and Molecular Biology, Ontario Cancer Institute/Princess Margaret Hospital, University of Toronto, Canada.
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S
McCracken
S
S
Leung
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Bosselut
J
J
Ghysdael
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NG
Miyamoto
D001483:Base Sequence; D001665:Binding Sites; D002478:Cells, Cultured; D006367:HeLa Cells; D006801:Humans; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides; D011401:Promoter Regions, Genetic; D011505:Protein-Tyrosine Kinases / Q000235:genetics*; D050784:Proto-Oncogene Protein c-ets-1; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D050783:Proto-Oncogene Proteins c-ets; D020598:Proto-Oncogene Proteins c-myb; D014157:Transcription Factors / Q000378:metabolism*
C494041:ETS1 protein, human; D009838:Oligodeoxyribonucleotides; D050784:Proto-Oncogene Protein c-ets-1; D011518:Proto-Oncogene Proteins; D050783:Proto-Oncogene Proteins c-ets; D020598:Proto-Oncogene Proteins c-myb; D014157:Transcription Factors; D011505:Protein-Tyrosine Kinases; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck)