An episomal var promoter is silenced by adjacent promoters. (A) Schematic maps of vectors. Plasmid constructs carry either a ‘free' var promoter (pVLH) or a var promoter paired with a var intron promoter (pVLH/int), the hrp2 promoter (pVLH/hrp), the hsp86 promoter (pVLH/hsp86) or the rRNA promoter (pVLH/rRNA). Luciferase activity was measured in transfected synchronized parasites (B) before S phase, or (C) after proceeding through at least one S phase. S-phase dependence was determined as described previously (Calderwood et al, 2003). Error bars represent calculated standard deviations. hrp2, histidine-rich protein 2; hsp86, heat-shock protein 86; rRNA, ribosomal RNA.