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  • Poster presentation
  • Open Access

Placement of p6pol between tandem repeat HIV-1 protease domains reduces Gag cleavage efficiency

  • 1,
  • 2 and
  • 1, 2
Retrovirology201310 (Suppl 1) :P98

  • Published:


  • Virus Assembly
  • Extra Copy
  • Infection Assay
  • Protease Domain
  • Ribosomal Frameshift


HIV-1 protease (PR) is encoded by pol, which is initially translated as a Pr160 gag-pol polyprotein by a ribosomal frameshift event [1]. Pr160 gag-pol is incorporated into virions via interactions with assembling Pr55 gag . The PR-mediated proteolytic cleavage of Pr55 gag and Pr160 gag-pol , known as virus maturation, is essential for the acquisition of viral infectivity. Within the Gag-Pol, the p6gag is truncated and is replaced by a transframe domain referred to as p6* or p6pol. Removal of p6pol improves Gag-Pol autoprocessing, suggesting that p6pol is involved in regulation of PR activation [2]. However, overlapping of p6gag/p6pol reading frame hampers generic approach to studying p6pol biological function. To assess the p6pol contribution to PR-mediated virus maturation without affecting p6gag reading frame, we introduced an extra copy of p6pol-PR or PR coding sequence at the PR C-terminus.

Materials and methods

PCR-amplified p6pol-PR or PR fragments were inserted at the PR C-terminus of an env-deleted HIV-1 proviral vector. Each of the constructs was transiently expressed in 293T cells, and virus assembly and processing were analyzed by Western blot. Virus infectivity was determined by a single-cycle infection assay.


HIV-1 mutants containing tandem repeat PR domains were severely defective in virus particle production due to enhanced Gag cleavage. Inactivation of the proximal PR affects Gag cleavage efficiency at a greater extent than inactivation of the distal PR. Placement of p6pol between the tandem repeat PR domains resulted in diminished Gag cleavage efficiency.


Our study indicates that the Gag cleavage enhancement effect incurred by over-expressed HIV-1 PR is reduced following the placement of p6pol between the tandem repeat PR domains. This supports the proposal that p6pol plays a negative role in the process of PR activation.

Authors’ Affiliations

Institute of Clinical Medicine, National Yang-Ming University School of Medicine, Taipei, Taiwan
Department of Medical Research and Education, Taipei Veterans General Hospital, Taipei, Taiwan


  1. Jacks T, Power MD, Masiarz FR, Luciw PA, Barr PJ, Varmus HE: Characterization of ribosomal frameshifting in HIV-1 gag-pol expression. Nature. 1988, 331: 280-283. 10.1038/331280a0.View ArticlePubMedGoogle Scholar
  2. Partin K, Zybarth G, Ehrlich L, DeCrombrugghe M, Wimmer E, Carter C: Deletion of sequences upstream of the proteinase improves the proteolytic processing of human immunodeficiency virus type 1. Proc Natl Acad Sci USA. 1991, 88: 4776-4780. 10.1073/pnas.88.11.4776.PubMed CentralView ArticlePubMedGoogle Scholar


© Chou et al; licensee BioMed Central Ltd. 2013

This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.