THE INTERACTION OF THE REVERSE-TRANSCRIPTASE OF HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 WITH 3'-TERMINALLY MISPAIRED DNA

The extension of mismatched S'-termini of DNA was implicated as a majo r determinant that contributes to the low fidelity of the human immuno deficiency virus type 1 (HIV-1) reverse transcriptase (RT). However, H IV-1 RT exhibits variations in its comparative efficiency to extend di fferent 3'-mismatched base pairs that can result either from the diffe rences in the binding capacity of the enzyme to various mispaired DNAs or from differences in the rate of extension of mispairs by a DNA-bou nd enzyme. In the current study we have examined the interaction of HI V-1 RT with mispaired template-primer 3'-termini, using a gel retardat ion assay. HIV-1 RT was found to bind mismatched template-primers with purine-pyrimidine (i.e., A . C) and purine-purine (i.e., A . A and A . G) 3'-terminal mispairs to about the same extent. Hence, HIV-1 RT ca n be considered (in addition to its other basic features) as a 3'-mism atched DNA binding protein. The stability of the complexes formed betw een HIV-1 RT and the mismatched template-primers tested seems to be un affected significantly by neighboring sequences and by the presence of the next complementary dNTP. Thus, the dissimilarities observed previ ously in extension frequencies in the extension of 3'-terminal mismatc hes are likely to be due to an inherent property of the HIV-1 RT. The fact that HIV-1 RT binds 3'-mismatch-containing template-primers sugge sts that unextended mismatched DNA can undergo a rebinding process fol lowed by a 3'-mismatch extension, contributing to further understandin g of the low fidelity characteristic of HIV-1 RT. It is possible, ther efore, that the interaction of the RT with the DNA may constitute an a dditional suitable target for the development of specific anti-HIV-1 R T drugs. (C) 1996 Academic Press, Inc.