A reiterative mode of DNA synthesis adopted by HIV-1 reverse transcriptase after a misincorporation

Amplification of oligonucleotide repeats is a major cause of variability and instability of genomes. This phenomenon is probably due to an aberration in the copying process of polymerases. We show here that in the presence of MnCl2, mismatch formation commits HIV-1 reverse transcriptase to a new mode of DNA synthesis which generates repetitive products. This activity is distinct from terminal transferase since it requires specific DNA motifs in the template. This mechanism, which is processive, also works on homologous RNA templates where it generates reiterative products more than 150 nucleotides long. The corresponding mechanism, which involves extensive primer misalignment, is strikingly similar to that postulated for telomerases.