FIG. 3.
Transactivation of the IL-13 promoter by the HTLV-1 Tax protein. The IL-13 promoter was inserted into a luciferase indicator construct (pGL3 Basic). (A) Overview of the IL-13 promoter deletion variants used. The deleted sequences are indicated. (B) Tax transactivation of the IL-13 promoter by at least two separate pathways. Jurkat T lymphocytes were transfected with the IL-13 promoter (IL13P) in the presence of an empty expression vector (pcDNA3.1), TaxWT, a single Tax mutant (M7, M22, or M47), or a combination of two mutants (M22+M47). Luciferase activity was determined and normalized to the negative control (pcDNA3.1). Neither M22 nor M47 alone was able to fully transactivate the promoter, but the combination of both was able to do so. The bars represent the means from eight independent experiments and the standard deviations. (C) Stimulation of promoter variants with 5′ deletions by Tax. The fold stimulation of luciferase activity in the presence of Tax is indicated. The bars represent the means and standard deviations from four independent experiments. (D) Requirement of two promoter regions for Tax stimulation. The indicated internal promoter deletion variants were cotransfected with pcTax or an empty vector (pcDNA3.1); the resulting luciferase activity was normalized to IL13P. Deletion of nt −134 to −121 resulted in a severe reduction of transactivation, deletions within nt −106 to −98 resulted in a moderate reduction, and the variant with a double deletion was not inducible by Tax. The bars represent the means and standard deviations from six independent experiments.