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Journal of Virology, September 2005, p. 11952-11961, Vol. 79, No. 18
0022-538X/05/$08.00+0     doi:10.1128/JVI.79.18.11952-11961.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

Virion Instability of Human Immunodeficiency Virus Type 1 Reverse Transcriptase (RT) Mutated in the Protease Cleavage Site between RT p51 and the RT RNase H Domain

Michael E. Abram and Michael A. Parniak*

University of Pittsburgh School of Medicine, Division of Infectious Diseases, Pittsburgh, Pennsylvania 15261

Received 11 February 2005/ Accepted 18 June 2005

Each of the human immunodeficiency virus type 1 (HIV-1) pol-encoded enzymes, protease (PR), reverse transcriptase (RT), and integrase (IN), is active only as a dimer (or higher-order oligomer in the case of IN), but only RT comprises subunits of different masses. RT is a heterodimer of 66-kDa and 51-kDa subunits. The latter is formed by HIV PR-catalyzed cleavage of p66 during virion maturation, resulting in the removal of the RNase H (RNH) domain of a p66 subunit. In order to study the apparent need for RT heterodimers in the context of the virion, we introduced a variety of mutations in the RT p51-RNH protease cleavage site of an infectious HIV-1 molecular clone. Surprisingly, rather than leading to virions with increased RT p66 content, most of the mutations resulted in significantly attenuated virus that contained greatly decreased levels of RT that in many cases was primarily p51 RT. IN levels were also reduced in several mutants. However, most mutants showed normal levels of the Pr160gag-pol precursor polyprotein, suggesting that reduced virion RT arose from proteolytic instability rather than decreased incorporation. Mutant virion p24 Gag levels were equivalent to wild type, indicating that Gag incorporation and processing were not affected. Repeated passage of MT-2 cells exposed to mutant viruses led to the appearance of virus with improved replication capacity; these virions contained normally processed RT at near-wild-type levels. These results imply that additional proteolytic processing of RT to the p66/p51 heterodimer is essential to provide proteolytic stability of RT during HIV-1 maturation.

* Corresponding author. Mailing address: University of Pittsburgh School of Medicine, Division of Infectious Diseases, Scaife Hall, Suite S817, 3550 Terrace Street, Pittsburgh, PA 15261. Phone: (412) 648-1927. Fax: (412) 648-8521. E-mail: parniakm{at}msx.dept-med.pitt.edu.

Journal of Virology, September 2005, p. 11952-11961, Vol. 79, No. 18
0022-538X/05/$08.00+0     doi:10.1128/JVI.79.18.11952-11961.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

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