title: HIV-1 Protease in the Fission Yeast Schizosaccharomyces pombe.
abstract: BACKGROUND
  HIV-1 protease (PR) is an essential viral enzyme. Its primary function is to proteolyze the viral Gag-Pol polyprotein for production of viral enzymes and structural proteins and for maturation of infectious viral particles. Increasing evidence suggests that PR cleaves host cellular proteins. However, the nature of PR-host cellular protein interactions is elusive. This study aimed to develop a fission yeast (Schizosaccharomyces pombe) model system and to examine the possible interaction of HIV-1 PR with cellular proteins and its potential impact on cell proliferation and viability.
  
  
  RESULTS
  A fission yeast strain RE294 was created that carried a single integrated copy of the PR gene in its chromosome. The PR gene was expressed using an inducible nmt1 promoter so that PR-specific effects could be measured. HIV-1 PR from this system cleaved the same indigenous viral p6/MA protein substrate as it does in natural HIV-1 infections. HIV-1 PR expression in fission yeast cells prevented cell proliferation and induced cellular oxidative stress and changes in mitochondrial morphology that led to cell death. Both these PR activities can be prevented by a PR-specific enzymatic inhibitor, indinavir, suggesting that PR-mediated proteolytic activities and cytotoxic effects resulted from enzymatic activities of HIV-1 PR. Through genome-wide screening, a serine/threonine kinase, Hhp2, was identified that suppresses HIV-1 PR-induced protease cleavage and cell death in fission yeast and in mammalian cells, where it prevented PR-induced apoptosis and cleavage of caspase-3 and caspase-8.
  
  
  CONCLUSIONS
  This is the first report to show that HIV-1 protease is functional as an enzyme in fission yeast, and that it behaves in a similar manner as it does in HIV-1 infection. HIV-1 PR-induced cell death in fission yeast could potentially be used as an endpoint for mechanistic studies, and this system could be used for developing a high-throughput system for drug screenings.
authors.affiliation: Department of Pathology, University of Maryland Medical School, Baltimore, Maryland, United States of America.
authors.forename: Zsigmond
authors.initials: Z
authors.lastname: Benko
authors.affiliation: Chicago Memorial Institute for Education and Research, Northwestern University Feinberg School of Medicine, Chicago, Illinois, United States of America.
authors.forename: Robert T
authors.initials: RT
authors.lastname: Elder
authors.affiliation: Department of Pathology, University of Maryland Medical School, Baltimore, Maryland, United States of America.
authors.forename: Ge
authors.initials: G
authors.lastname: Li
authors.affiliation: Department of Pathology, University of Maryland Medical School, Baltimore, Maryland, United States of America.
authors.forename: Dong
authors.initials: D
authors.lastname: Liang
authors.affiliation: Department of Pathology, University of Maryland Medical School, Baltimore, Maryland, United States of America.|Department of Microbiology-Immunology, University of Maryland Medical School, Baltimore, Maryland, United States of America.|Institute of Human Virology, University of Maryland Medical School, Baltimore, Maryland, United States of America.
authors.forename: Richard Y
authors.initials: RY
authors.lastname: Zhao
mesh_terms: D016333:HIV Protease / Q000378:metabolism*; D017320:HIV Protease Inhibitors / Q000494:pharmacology; D019469:Indinavir / Q000494:pharmacology; D018384:Oxidative Stress; D012568:Schizosaccharomyces / Q000187:drug effects / Q000201:enzymology*
chemical_list: D017320:HIV Protease Inhibitors; D019469:Indinavir; D016333:HIV Protease; C514803:p16 protease, Human immunodeficiency virus 1