The decrease in nucleoside analog incorporation  by HIV-1 RT in the presence of polyamines.

M. Bakhanashvili,  E. Novitsky  and G. Rahav. Unit of  Infectious Diseases, Sheba Medical Center, Tel-Hashomer, 52621 (Israel).

Background: HIV-1 RT is an important target for antiretroviral therapy.  Nucleoside analogues (NA), that inhibit HIV replication, exert their effect by incorporation at the  3¢ end of the growing DNA chain by the enzyme, thereby terminating chain extension and inhibiting replication of the virus. Our recent studies revealed that misincorporation reactions carried out by HIV-1 RT in the presence of polyamines (e.g. putrescine, spermidine and spermine) shows the increase in  misincorporation fidelity of the enzyme. In the present study we further investigated the role of polyamines in incorporation of NA. Material and Methods: The ability of recombinant HIV-1 RT to incorporate NA- ddATP into DNA was evaluated with both RNA/DNA and DNA/DNA template-primers in the absence and presence of all three polyamines using primer extension assays. Results: The results demonstrate a substantial decrease in incorporation of nucleoside analogs, e.g. ddATP by HIV-1 RT with both RNA/DNA and DNA/DNA substrates in the presence of  all three polyamines tested: spermine, spermidine or putrescine. Conclusion: Decrease in the incorporation of nucleoside analogs into DNA leads to reduction in antiviral effect. The fact, that the HIV-1 RT in the presence of polyamines displays lower efficiency of incorporation of nucleoside analogs, raise the possibility that the resistance to anti-retroviral NAs, in part, can involve the participation of cellular factors.