Exploitation of a rapid and sensitive assay to analyse transactivation of the human immunodeficiency virus type 1 (HIV-1) long terminal repeat

Transregulation of the promoter within the 5' long terminal repeat (LTR) of the human immunodeficiency virus (HIV) provirus determines the level of replication of HIV in latently, persistently or acutely infected cells. To measure rapidly the degree of transactivation of the HIV-1 LTR by various cellular and viral effectors, stably transformed cell lines containing integrated copies of the HIV LTR promoter (-122 to +80, relative to the major mRNA cap site) linked to the Escherichia coli lacZgene were prepared by co-selection for pSV2neo-mediated G418 resistance. One cell clone, RS 3/7, containing about 40 integrated copies of the recombinant LTR-lacZ gene was analysed further. RS 3/7 cells expressed high levels of beta-galactosidase in response to co-transfection with plasmids expressing the HIV-1 transactivator, tat, infection with low multiplicities of herpes simplex virus type 1 (HSV-1), transfection with a plasmid expressing the HSV-1 immediate-early (IE) protein, ICPO, and by incubation with medium containing sodium butyrate. beta-galactosidase activity was also induced by incubation of RS 3/7 cells with medium containing full length tat polypeptide. The cysteine analogue, D-penicillamine, previously reported as a potent inhibitor of tat-mediated transactivation (Chandra et al., 1988), was of limited efficacy in RS 3/7 cells transfected with tat-expressing plasmids. This cell line will be of value in identifying additional transactivators of the HIV-1 LTR, and in the selection of inhibitors of such effectors.