Nucleic Acids Research Advance Access published online on December 23, 2008
Nucleic Acids Research, doi:10.1093/nar/gkn1015
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The A-rich RNA sequences of HIV-1 pol are important for the synthesis of viral cDNA
1Centre for Virology, Macfarlane Burnet Institute for Medical Research and Public Health, Melbourne, Victoria, Australia, 2Department of Microbiology, 3Department of Biochemistry and Molecular Biology, Monash University, Melbourne, Victoria, Australia, 4Architecture et Réactivité de l’ARN, Université de Strasbourg, CNRS, IBMC, Strasbourg cedex, France, 5Center for Cancer Research Nanobiology Program, CCR, National Cancer Institute, Frederick, MD, 6Institute for Molecular Virology, University of Wisconsin, Madison, WI, USA, 7Victorian Infectious Diseases Reference Laboratory (VIDRL), Melbourne, Victoria, Australia and 8Vaccine Research Center, National Institute of Allergy and Infectious Disease, National Institutes of Health, Bethesda, MD, USA
*To whom correspondence should be addressed. Tel: +61 3 9282 2217; Fax: +61 3 9282 2100; Email: mak{at}burnet.edu.au
Received November 11, 2008. Revised December 2, 2008. Accepted December 4, 2008.
The bias of A-rich codons in HIV-1 pol is thought to be a record of hypermutations in viral genomes that lack biological functions. Bioinformatic analysis predicted that A-rich sequences are generally associated with minimal local RNA structures. Using codon modifications to reduce the amount of A-rich sequences within HIV-1 genomes, we have reduced the flexibility of RNA sequences in pol to analyze the functional significance of these A-rich ‘structurally poor’ RNA elements in HIV-1 pol. Our data showed that codon modification of HIV-1 sequences led to a suppression of virus infectivity by 5–100-fold, and this defect does not correlate with, viral entry, viral protein expression levels, viral protein profiles or virion packaging of genomic RNA. Codon modification of HIV-1 pol correlated with an enhanced dimer stability of the viral RNA genome, which was associated with a reduction of viral cDNA synthesis both during HIV-1 infection and in a cell free reverse transcription assay. Our data provided direct evidence that the HIV-1 A-rich pol sequence is not merely an evolutionary artifact of enzyme-induced hypermutations, and that HIV-1 has adapted to rely on A-rich RNA sequences to support the synthesis of viral cDNA during reverse transcription, highlighting the utility of using ‘structurally poor’ RNA domains in regulating biological process.
The authors wish it to be known that, in their opinion, the first two authors should be regarded as joint First Authors.