Fig. 4

Transcriptional regulation of the human immunodeficiency virus type 1 (HIV-1) long terminal repeat (LTR) is mediated by RATS, NFAT and NFκB elements. Histogram of mean cloramphenicol acetyl transferase (CAT) activity of 3 to 5 independent injection series. The basal activity displayed by each target gene in each series was set to 1 (horizontal line). CAT expression in the presence of protein was normalized to the basal level of each experimental group, averaged (columns) and the standard error mean determined (brackets). Extracts from resting peripheral T lymphocytes reduce target gene expression (black columns) and further addition of extracts from 4 hr-stimulated cells reestablishes CAT expression (hatched columns). (A) The target promoters contain an Sp1 site between the cis-acting element tested and the TATA box. (B) No Sp1 site is present in the ΔSp1 target promoters (see Fig. 1). pSV2-CAT under the control of an SV40 promoter served as a control.