FIG. 1.

Effects of NF-κB and Sp1 on the activity of integrated HIV-1 LTRs. (A) Schematic representation of the WT-, KBmt-, and DS-LTR CAT constructs. The LTR (U3, R, and U5) and gag leader sequence (GLS) are represented by open rectangles. Binding sites for the NF-κB, Sp1, TFIID (TATA box), AP-1, AP-3-like, and DBF1 transcription factors are shown. The transcription initiation site is indicated by the arrow at the junction between in U3 and R sites. In the DS-LTR, the regulatory elements downstream of the transcription start site (AP-1, AP-3, DBF1, and the downstream Sp1) were deleted and an unrelated sequence (filled rectangle) was inserted between U5 and the CAT gene. (B) CAT activities in unstimulated (Basal) or transfected (1 μg of Sp1 or NF-κB expression vector) WT3, KB1, and DS2 cells. (C) HeLa cells were transiently transfected with WT-, DS- or KBmt-LTR-CAT reporter plasmid alone (Basal) or along with 1 μg of vector expressing Sp1 or NF-κB as indicated at the bottom. At 24 h posttransfection, CAT activity was determined in cell lysates and expressed as percent acetylated chloramphenicol (% acetylation). The bars show the results from a representative transfection experiment; the numbers above the bars indicate average fold induction.