Figure 2.

Effects of wild-type λcI and λcI superactivators on transcription in the presence of the α-σ⁷⁰ chimera. (A) SF1 cells harboring the indicated plasmids were assayed for β-galactosidase activity. pACYC-derived plasmids encoded λcI (pACλcI), λcISa109 [pACλcI(Sa109)], or λcISa104 [pACλcI(Sa104)]; pBR322-derived plasmids encoded either the α-σ⁷⁰ chimera (pBRα-σ⁷⁰) or wild-type α (pBRα). (B) Primer extension analysis of transcripts produced from plac O_R2–55/Cons-35 with wild-type λcI or λcI superactivators in the presence of the α-σ⁷⁰ chimera. Total RNA was isolated from SF1 cells harboring plasmids encoding the indicated proteins, and the primer extension analysis was done by using a primer complementary to the lacZ transcript produced by the plac O_R2–55/Cons-35 promoter. Primer extension products produced by correctly initiated transcripts are indicated by +1. Excess unincorporated primer is shown in the lower panel.