Cell cycle-dependent switch of up-and down-regulation of human hsp70 gene expression by interaction between c-Myc and CBF/NF-Y.
A CCAAT box-binding protein subunit, CBF-C/NF-YC, was cloned as a protein involved in the c-Myc complex formed on the G(1)-specific enhancer in the human hsp70 gene. CBF-C/NF-YC directly bound to c-Myc in vitro and in vivo in cultured cells. The CBF/NF-Y.c-Myc complex required the HSP-MYC-B element as well as CCAAT in the hsp70 G(1)-enhancer, while the purified CBF subunits recognized only CCAAT even in the presence of c-Myc. Both the HSP-MYC-B and CCAAT elements were also required for the enhancer activity. In transient transfection experiments, the CBF/NF-Y.c-Myc complex, as well as transcription due to the G(1)-enhancer, was increased by the introduction of c-Myc at low doses but decreased at high doses. The repression of both complex formation and transcription by c-Myc at high doses was abrogated by the introduction of CBF/NF-Y in a dose-dependent manner. Furthermore, the CBF/NF-Y.c-Myc complex bound to the G(1)-enhancer appeared in the early G(1) phase of the cell cycle when c-Myc was not higly expressed and gradually disappeared after the c-Myc expression reached its maximum. The results indicate that the cell cycle-dependent expression of the hsp70 gene is regulated by the intracellular amount of c-Myc through the complex formation states between CBF/NF-Y and c-Myc.
Taira
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Graduate School of Pharmaceutical Sciences, Hokkaido University, Kita-ku, Sapporo 060, Japan.
Sawai
M
M
Ikeda
M
M
Tamai
K
K
Iguchi-Ariga
S M
SM
Ariga
H
H
D016475:3T3 Cells; D000818:Animals; D001483:Base Sequence; D022762:CCAAT-Enhancer-Binding Proteins; D016466:CHO Cells; D002453:Cell Cycle; D006224:Cricetinae; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000502:physiology*; D005786:Gene Expression Regulation; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics*; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D016271:Proto-Oncogene Proteins c-myc / Q000502:physiology*; D011817:Rabbits; D014158:Transcription, Genetic
D022762:CCAAT-Enhancer-Binding Proteins; D004268:DNA-Binding Proteins; D018840:HSP70 Heat-Shock Proteins; D016271:Proto-Oncogene Proteins c-myc; D004247:DNA