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Molecular and Cellular Biology, December 1998, p. 7009-7019, Vol. 18, No. 12
Department of Molecular Biology, The Lerner
Research Institute, The Cleveland Clinic Foundation, Cleveland,
Ohio 44195
Received 8 May 1998/Returned for modification 10 July 1998/Accepted 2 September 1998
The roles of protein dimerization and double-stranded RNA (dsRNA)
binding in the biochemical and cellular activities of PKR, the
dsRNA-dependent protein kinase, were investigated. We have previously
shown that both properties of the protein are mediated by the same
domain. Here we show that dimerization is mediated by hydrophobic
residues present on one side of an amphipathic
0270-7306/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Requirement of PKR Dimerization Mediated by
Specific Hydrophobic Residues for Its Activation by
Double-Stranded RNA and Its Antigrowth Effects in
Yeast
-helical structure
within this domain. Appropriate substitution mutations of residues on
that side produced mutants with increased or decreased dimerization
activities. Using these mutants, we demonstrated that dimerization is
not essential for dsRNA binding. However, enhancing dimerization
artificially, by providing an extraneous dimerization domain, increased
dsRNA binding of both wild-type and mutant proteins. In vitro, the
dimerization-defective mutants could not be activated by dsRNA but were
activated normally by heparin. In Saccharomyces cerevisiae,
unlike wild-type PKR, these mutants could not inhibit cell growth and
the dsRNA-binding domain of the dimerization-defective mutants could
not prevent the antigrowth effect of wild-type PKR. These results
demonstrate the biological importance of the dimerization properties of PKR.
*
Corresponding author. Mailing address: Department of
Molecular Biology, The Cleveland Clinic Foundation, 9500 Euclid Ave., NC20, Cleveland, OH 44195. Phone: (216) 444-0636. Fax: (216) 444-0512. E-mail: seng{at}cesmtp.ccf.org.
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