c-Myb-induced trans-activation mediated by heat shock elements without sequence-specific DNA binding of c-Myb.
The c-myb proto-oncogene product (c-Myb) can transactivate the human hsp70 promoter in a transient cotransfection assay. The present studies have demonstrated that the heat shock element (HSE) in the hsp70 promoter mediates trans-activation by c-Myb. Mutagenesis of the DNA sequence in HSE indicated that the NGAAN motif is necessary for not only the heat shock response but also the c-Myb-induced trans-activation. The HSE in the hsp70 promoter does not contain a c-Myb-binding site, implying that the sequence-specific DNA binding of c-Myb is not required for the HSE-dependent trans-activation by c-Myb. We had demonstrated that a disruption of the leucine zipper motif in the central portion of the c-Myb molecule increased the degree of c-Myb-induced trans-activation of the promoter containing c-Myb-binding sites, suggesting that a putative inhibitor binds to c-Myb through this leucine zipper (Kanie-Ishii, C., MacMillan, E. M., Nomura, T., Sarai, A., Ramsay, R. G., Aimoto, S., Ishii, S., and Gonda, T. J. (1992) Proc. Natl. Acad. Sci. U.S.A. 89, 3088-3092). However, disruption of the leucine zipper in c-Myb abolished the HSE-dependent trans-activation by c-Myb, whereas deletion of the transcriptional activation domain containing acidic amino acids in c-Myb did not abolish the HSE-dependent trans-activation by c-Myb. These results suggest that c-HSEs by interacting with unidentified trans-acting factor(s) but not by a direct binding to the promoter through its DNA-binding domain.
Kanei-Ishii
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C
Laboratory of Molecular Genetics, Tsukuba Life Science Center, Institute of Physical and Chemical Research (RIKEN), Ibaraki, Japan.
Yasukawa
T
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Morimoto
R I
RI
Ishii
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D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002460:Cell Line; D002645:Chickens; D015500:Chloramphenicol O-Acetyltransferase / Q000096:biosynthesis / Q000378:metabolism; D002522:Chlorocebus aethiops; D004268:DNA-Binding Proteins / Q000378:metabolism*; D006360:Heat-Shock Proteins / Q000235:genetics*; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides; D009857:Oncogenes; D010957:Plasmids; D011401:Promoter Regions, Genetic; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D020598:Proto-Oncogene Proteins c-myb; D011519:Proto-Oncogenes; D015183:Restriction Mapping; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014162:Transfection
D004268:DNA-Binding Proteins; D006360:Heat-Shock Proteins; C000715470:MAS1 protein, human; D009838:Oligodeoxyribonucleotides; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins; D020598:Proto-Oncogene Proteins c-myb; D015500:Chloramphenicol O-Acetyltransferase