Figure 4.

Examination of the role of promoter elements in bidirectional transcription initiation. (A) Construction of dual reporter plasmids utilizing a shared promoter region in Giardia. Bidirectional plasmid constructs were generated to create a dual reporter system that permits us to quantify bidirectional transcription and to more closely examine the roles of specific elements within Giardia promoters. We generated several reporter constructs that contain firefly and Renilla luciferase reporter genes in a head-to-head arrangement, separated by different promoter regulatory units of the alpha-2 tubulin promoter. (B) Quantitative measurements of bidirectional promoter strength for elements of the alpha-2 tubulin promoter. Luciferase assays were conducted in triplicate on parasites stably transfected with the dual reporter constructs. Firefly and Renilla luciferase activities were established at 100% in the control (S1 and S2) plasmids, and other measurements were calculated relative to these levels.