Recombination analysis and structure prediction show correlation between breakpoint clusters and RNA hairpins in the pol gene of human immunodeficiency virus type 1 unique recombinant forms

1 Department of Clinical Sciences ‘L. Sacco’, University of Milan, Milan, Italy 2 Department of Molecular Biology, University of Siena, Siena, Italy Correspondence Andrea Galli Andrea.Galli{at}unimi.it Recombination is recognized as a primary force in human immunodeficiency virus type 1 (HIV-1) evolution, increasing viral diversity through reshuffling of genomic portions. The strand-switching activity of reverse transcriptase is required to complete HIV-1 replication and can occur randomly throughout the genome, leading to viral recombination. Some recombination hotspots have been identified and found to correlate with RNA structure or sequence features. The aim of this study was to evaluate the presence of recombination hotspots in the pol gene of HIV-1 and to assess their correlation with the underlying RNA structure. Analysis of the recombination pattern and breakpoint distribution in a group of unique recombinant forms (URFs) detected two recombination hotspots in the pol region. Two stable and conserved hairpins were consistently predicted corresponding to the identified hotspots using six different RNA-folding algorithms on the URF parental strains. These findings suggest that such hairpins may play a role in the higher recombination rates detected at these positions. The GenBank/EMBL/DDBJ accession numbers for the sequences determined in this study are EF488562–EF488607.