Nucleic Acids Research Advance Access published online on October 11, 2007
Nucleic Acids Research, doi:10.1093/nar/gkm767
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Trans-lesion synthesis and RNaseH activity by reverse transcriptases on a true abasic RNA template
Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, CH-3012 Bern, Switzerland
* To whom correspondence should be addressed. Tel: +41 0 31 631 4355; Fax: +41 0 31 631 3422; Email: leumann{at}ioc.unibe.ch
Received August 16, 2007. Revised September 10, 2007. Accepted September 11, 2007.
While much is known about abasic DNA, the biological impact of abasic RNA is largely unexplored. To test the mutagenic potential of this RNA lesion in the context of retroviruses, we synthesized a 31-mer oligoribonucleotide containing an abasic (rAS) site and used it as a template for studying DNA primer extension by HIV-1, avian myeloblastosis virus (AMV) and moloney murine leukemia virus (MMLV) reversed transcriptases (RT). We found that trans-lesion synthesis readily takes place with HIV-1 RT and to a lesser extent with AMV RT while MMLV RT aborts DNA synthesis. The preference of dNTP incorporation follows the order A
G > CT and thus obeys to the ‘A-rule’. In the case of HIV-1 RT, we measured the kinetic data of dNTP incorporation and compared it to abasic DNA. We found that A-incorporation is only 2-fold slower relative to a matched (undamaged) RNA template while it is 7-fold slower in the case of DNA. Furthermore, there is less discrimination in incorporation between the four dNTPs in the case of abasic RNA compared to abasic DNA. These experiments clearly point to a higher promiscuity of lesion bypass on abasic RNA. Given their known higher chemical stability, such rAS sites can clearly contribute to (retro)viral evolution.