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Journal of Virology, August 2007, p. 8192-8200, Vol. 81, No. 15
0022-538X/07/$08.00+0 doi:10.1128/JVI.00426-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.
Protein Kinase PKR Plays a Stimulus- and Virus-Dependent Role in Apoptotic Death and Virus Multiplication in Human Cells
Ping Zhang and
Charles E. Samuel*
Department of Molecular, Cellular and Developmental Biology and Biomolecular Sciences and Engineering Program, University of California, Santa Barbara, California 93106
Received 27 February 2007/
Accepted 10 May 2007
The protein kinase regulated by double-stranded RNA (dsRNA), PKR, is implicated in a range of biologic processes, including apoptotic death and interferon antiviral responses, based in part on studies with mouse cells genetically deficient in Pkr. To test the role of the PKR protein in human cells, an RNA interference silencing strategy was used to generate stable HeLa cell lines with less than 2% of the PKR protein (PKR deficient) compared to either parental or control knockdown HeLa lines. Phosphorylation of the
subunit of eukaryotic initiation factor 2 on serine 51 was not detectably increased in response to dsRNA in PKR-deficient HeLa cells but was elevated severalfold in PKR-sufficient cells. PKR-deficient cells displayed reduced dsRNA-induced apoptosis compared to PKR-sufficient cell lines, whereas tumor necrosis factor alpha (TNF-
)-induced apoptosis was comparable between the HeLa lines. NF-
B was activated to a comparable extent in PKR-deficient and PKR-sufficient HeLa cells upon treatment with either dsRNA or TNF-
. The antiviral response against vesicular stomatitis virus was reduced in interferon-treated PKR-deficient compared to PKR-sufficient HeLa cells. However, the growth of two human viruses, adenovirus and reovirus, was unaffected by the PKR knockdown. Surprisingly, the yield of mutant adenovirus that fails to encode VAI RNA was not enhanced in PKR-deficient cells, indicating the importance of host factors in addition to PKR in conferring the VAI RNA phenotype.
* Corresponding author. Mailing address: Department of Molecular, Cellular and Developmental Biology and Biomolecular Sciences and Engineering Program, University of California, Santa Barbara, CA 93106. Phone: (805) 893-3097. Fax: (805) 893-4724. E-mail:
samuel{at}lifesci.lscf.ucsb.edu
Published ahead of print on 23 May 2007.
Journal of Virology, August 2007, p. 8192-8200, Vol. 81, No. 15
0022-538X/07/$08.00+0 doi:10.1128/JVI.00426-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.
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