FIG. 5.

Analysis of HERV-K-T47D putative LTR promoter activity in T47D cells. (A) pBL-HERV reporter constructs used for luciferase expression assays. The putative LTR 1.2-kb PCR fragment (Fig. 1, fragment BB1.2) was cloned in the sense (pBL-BB1.2s) and the antisense (pBL-BB1.2as) orientations into the luciferase expression vector pBL. As controls, plasmid pBL-SH1.5gag with the insert (SH1.5gag, Fig. 1) and pBL-HERV-H containing the HERV-H LTR promoter of H6 (7) were similarly constructed. MCS, multiple cloning site; SV-40, simian virus 40. (B) Transient expression in T47D cells of HERV-pBL luciferase reporter constructs. T47D cells were transiently transfected according to standard procedures. The luciferase expression driven by the retroviral promoter was measured by a standardized luciferase assay and is shown as bar graphs representing relative promoter activity. All results shown are derived from triplicate experiments.