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Journal of Virology, November 2006, p. 10407-10418, Vol. 80, No. 21
0022-538X/06/$08.00+0 doi:10.1128/JVI.01212-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.
Michael P. Sherman,2,
Jana L. Blackett,1
Jason A. Neidleman,2
Christophe Kreis,2
Pamela Mundt,2
Samuel A. Williams,2
Maria Warmerdam,2
James Kahn,3
Frederick M. Hecht,3
Robert M. Grant,2
Carlos M. C. de Noronha,2
Andrew S. Weyrich,4
Warner C. Greene,2 and
Vicente Planelles1*
Division of Cellular Biology and Immunology, Department of Pathology, University of Utah School of Medicine, Salt Lake City, Utah 84132,1 Gladstone Institute of Virology and Immunology, San Francisco, California 94158,2 Positive Health Program, San Francisco General Hospital, San Francisco, California 94110,3 Program in Human Molecular Biology and Genetics, Department of Internal Medicine, University of Utah School of Medicine, Salt Lake City, Utah 841324
Received 9 June 2006/ Accepted 10 August 2006
The human immunodeficiency virus type 1 (HIV-1) viral protein R (Vpr) causes cell cycle arrest in G2. Vpr-expressing cells display the hallmarks of certain forms of DNA damage, specifically activation of the ataxia telangiectasia mutated and Rad3-related kinase, ATR. However, evidence that Vpr function is relevant in vivo or in the context of viral infection is still lacking. In the present study, we demonstrate that HIV-1 infection of primary, human CD4+ lymphocytes causes G2 arrest in a Vpr-dependent manner and that this response requires ATR, as shown by RNA interference. The event leading to ATR activation in CD4+ lymphocytes is the accumulation of replication protein A in nuclear foci, an indication that Vpr likely induces stalling of replication forks. Primary macrophages are refractory to ATR activation by Vpr, a finding that is consistent with the lack of detectable ATR, Rad17, and Chk1 protein expression in these nondividing cells. These observations begin to explain the remarkable resilience of macrophages to HIV-1-induced cytopathicity. To study the in vivo consequences of Vpr function, we isolated CD4+ lymphocytes from HIV-1-infected individuals and interrogated the cell cycle status of anti-p24Gag-immunoreactive cells. We report that infected cells in vivo display an aberrant cell cycle profile whereby a majority of cells have a 4N DNA content, consistent with the onset of G2 arrest.
Published ahead of print on 6 September 2006.
These
authors contributed equally.
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