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Molecular and Cellular Biology, April 2007, p. 2910-2918, Vol. 27, No. 8
0270-7306/07/$08.00+0 doi:10.1128/MCB.02256-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.
Interferon Regulatory Factor 7 Is Activated by a Viral Oncoprotein through RIP-Dependent Ubiquitination
Leslie E. Huye ,3,
,
Shunbin Ning,3,
Michelle Kelliher,4 and
Joseph S. Pagano1,2,3*
Department of Medicine,1
and Department of Microbiology and Immunology, Lineberger Comprehensive Cancer Center,2
School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599,3
Department of Cancer Biology and Cancer Center, University of Massachusetts Medical School, Worcester, Massachusetts 016054
Received 1 December 2006/
Returned for modification 17 January 2007/
Accepted 2 February 2007
As a key mediator of type I interferon (IFN) (IFN-
/ß) responses, IFN regulatory factor 7 (IRF7) is essential to host immune defenses. Activation of IRF7 generally requires virus-induced C-terminal phosphorylation, which leads to its nuclear accumulation and activation of target genes. Here we use the Epstein-Barr virus (EBV) oncoprotein LMP1, which activates IRF7, to identify factors involved in IRF7 activation. We demonstrate for the first time that RIP activates IRF7 and that RIP and IRF7 interact under physiological conditions in EBV-positive Burkitt's lymphoma cells. We provide evidence that both RIP and IRF7 are ubiquitinated in these cells and that IRF7 preferentially interacts with ubiquitinated RIP. RIP is required for full activation of IRF7 by LMP1, with LMP1 stimulating the ubiquitination of RIP and its interaction with IRF7. Moreover, LMP1 stimulates RIP-dependent K63-linked ubiquitination of IRF7, which regulates protein function rather than proteasomal degradation of proteins. We suggest that RIP may serve as a general activator of IRF7, responding to and transmitting the signals from various stimuli, and that ubiquitination may be a general mechanism for enhancing the activity of IRF7.
* Corresponding author. Mailing address: Lineberger Comprehensive Cancer Center, University of North Carolina, Campus Box 7295, Chapel Hill, NC 27599. Phone: (919) 966-5907. Fax: (919) 966-9673. E-mail:
joseph_pagano{at}med.unc.edu
Published ahead of print on 12 February 2007.
These authors contributed equally to this work.
Present address: Center for Cell and Gene Therapy, Baylor College of Medicine, Houston, TX.
Molecular and Cellular Biology, April 2007, p. 2910-2918, Vol. 27, No. 8
0270-7306/07/$08.00+0 doi:10.1128/MCB.02256-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.
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