Cell Cycle-dependent Switch of Up- and Down-regulation of Human hsp70 Gene Expression by Interaction between c-Myc and CBF/NF-Y*
- Takahiro Taira‡,
- Madoka Sawai‡,
- Masako Ikeda§,
- Katsuyuki Tamai§,
- Sanae M. M. Iguchi-Ariga¶ and
- Hiroyoshi Ariga‡‖
- From the ‡Graduate School of Pharmaceutical Sciences,¶College of Medical Technology, Hokkaido University, Kita-ku, Sapporo 060, Japan, and §Ina Laboratories, MBL Co. Ltd., Ina 396, Japan
Abstract
A CCAAT box-binding protein subunit, CBF-C/NF-YC, was cloned as a protein involved in the c-Myc complex formed on the G1-specific enhancer in the human hsp70gene. CBF-C/NF-YC directly bound to c-Myc in vitro andin vivo in cultured cells. The CBF/NF-Y·c-Myc complex required the HSP-MYC-B element as well as CCAAT in the hsp70G1-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 G1-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 G1-enhancer appeared in the early G1 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.
Footnotes
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↵* This work was supported by grants-in-aid from the Ministry of Education, Science, Culture and Sports of Japan.The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
The nucleotide sequences of HSM-1/NF-YC and HSM-2 reported in this paper have been submitted to the GenBankTM/EBI Data Bank with accession numbers and , respectively.
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↵‖ To whom correspondence should be addressed: Graduate School of Pharmaceutical Sciences, Hokkaido University, Kita 12, Nishi 6, Kita-ku, Sapporo 060-0812, Japan. Tel.: 81-11-706-3745; Fax: 81-11-706-4988; E-mail: hiro@pharm.hokudai.ac.jp.
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↵1 T. Niki, submitted for publication.
- Abbreviations:
- CHO
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Chinese hamster ovary
- GALBD
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GAL4 DNA-binding domain
- GST
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glutathioneS-transferase
- MBP
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maltose-binding protein
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- Received February 12, 1999.
- Revision received May 17, 1999.
- The American Society for Biochemistry and Molecular Biology, Inc.
