A MUTATION IN INTEGRASE CAN COMPENSATE FOR MUTATIONS IN THE SIMIAN IMMUNODEFICIENCY VIRUS ATT SITE

Sequences at the left terminus of U3 in the left long terminal repeat (LTR) and at the right terminus of U5 in the right LTR are important f or integration of retroviral DNA, In the infectious pathogenic molecul ar clone of simian immunodeficiency virus strain mac239 (SIVmac239), 1 0 of the 12 terminal base pairs form an imperfect inverted repeat stru cture (5' TGGAAGGGATTT 3' [nucleotides 1 to 12] and 3' ACGATCCCTAAA 5' [nucleotides 10279 to 10268]). Nineteen different mutant forms of SIV mac239 proviral DNA with changes at one or more of the positions in ea ch of the 12-terminal-base-pair regions were constructed. Viral replic ation was severely or completely compromised with nine of these mutant s, Revertants appeared 40 to 50 days after transfection in two indepen dent experiments,vith mutant 7, which contained changes of AGG to TAC at positions 5 to 7 in U3 and TCC to GAA at positions 10275 to 10273 i n U5, Virus produced at these times from mutant 7 transfection replica ted upon reinfection with only a slight delay when compared to the wil d type. Sequence analysis of the LTR and integrase regions from infect ed cultures revealed two predominant changes: G to A at position 10275 in U5 and Glu to Lys at position 136 in integrase, Derivatives of clo ne 7 in which these changes were introduced individually and together were constructed by site-specific mutagenesis, Each change individuall y restored replication capacity only partially, However, the combinati on of both mutations restored replicative capacity to that of the orig inal revertants. These results indicate that changes in integrase can compensate for mutations in the terminal nucleotides of the SIV LTR. T he results further indicate that resistance to integrase inhibitors ma y include both integrase and LTR mutations.