Effects of long terminal repeat (LTR) of human immunodeficiency virus type 1 on the expression of gag gene in recombinant vaccinia viruses

To investigate the function of LTR in vaccinia virus, 6 recombinant viruses were constructed by inserting intact or serially truncated LTR together with their downstream of gag ORF of human immunodeficiency virus type 1 (HIV 1) into the vaccinia virus genome. Indirect fluorescence assay, Western blot and immunoenzyme assay showed that all the 6 recombinant vaccinia viruses expressed Gag protein, but the efficiency were significantly different. These results suggested that the function of each function domain in HIV 1 LTR exhibited distinct characteristics on gag gene expression in vaccinia virus: (1) The function of intact LTR on gag gene expression varied with the upstream poxvirus promoter; (2) NR sequence neither decreased nor increased the Gag protein exprssion level; (3) Enhancer sequence might not be recognized by recombinant vaccinia virus expression system; (4) TAR sequence enhanced Gag protein expression effectively; (5) U5 region and its downstream non translated sequence had little effect on