Reverse transcriptase and substrate dependence of the RNA hypermutagenesis reaction

Abstract

G→A hypermutation is a remarkable phenomenon resulting from retroviral reverse transcription In the presence of highly biased dNTP concentrations. Of the three reverse transcriptases (RTases) available, those of human immunodeficiency virus type 1 (HIV-1), avian myeloblastosls virus (AMV) and Moloney murine leukemia virus (MoMLV), the HI V-1 enzyme showed the greatest sensitivity to biased [dCTP]/[dTTP] ratios. The HI V-1 RTase was able to discriminate between dUTP, dITP and the four DNA precursors and was insensitive to pH. There was little preference for nucleotlde contexts. A few exceptionally modified sequences were found presumably resulting from G→A hypermutation and multiple strand transfer. This particular predilection of the HIV−1 and, by extrapolation, the lentiviral RTases towards G→A hypermutation suggests that the phenomenon may have contributed to the remarkably elevated A content of these retroviral genomes.