FUNCTIONAL-ANALYSIS OF SIMIAN IMMUNODEFICIENCY VIRUS SIVAGM LONG TERMINAL REPEAT

We have previously shown that long terminal repeats (LTRs) derived fro m various isolates of SIVAGM share a unique functional property. In th e absence of viral Tat, all SIVAGM LTRs act as much more efficient pro moters than any of the other LTRs derived from representative primate immunodeficiency viruses. In the presence of Tat, however, SIVAGM LTRs are activated relatively inefficiently. To map the elements that conf er these features on the SIVAGM LTR, a number of deletion mutants were constructed, and their promoter activities were determined using a ba cterial CAT gene as a marker. The results obtained indicated that vari ous elements located in the U3 region may contribute to the high basal promoter activity and that no negative elements are present in the re gion. The Tat-responsive sequence TAR was localized to the R region as observed for the other LTRs. A mutant carrying a single nucleotide de letion in this region completely lost responsiveness to Tat protein.