Transcription Activation at Class II CAP-Dependent Promoters: Two Interactions between CAP and RNA Polymerase

Class II CAP-dependent promoters, interacting with the RNAP ␣ subunit C-terminal domain (␣CTD) and facilitat-At Class I CAP-dependent promoters, interaction between the activating region and ␣CTD (and concomitant St. Louis, Missouri 63104 recruitment of RNAP to promoter DNA) appears to be the entire basis of transcription activation. Thus, at Class Summary I CAP-dependent promoters, removal of ␣CTD eliminates transcription activation (Igarashi and Ishihama, At Class II catabolite activator protein (CAP)-depen-1991). dent promoters, CAP activates transcription from a At Class II CAP-dependent promoters, the mechanism DNA site overlapping the DNA site for RNA polymer-of transcription activation is more complex. At Class ase. We show that transcription activation at Class II II CAP-dependent promoters, interaction between the CAP-dependent promoters requires not only the pre-activating region and ␣CTD overcomes an inhibitory ef-viously characterized interaction between an activat-fect of ␣CTD, facilitating the positioning of ␣CTD at a ing region of CAP and the RNA polymerase ␣ subunit neutral noninhibitory location on DNA (positions Ϫ74 to C-terminal domain, but also an interaction between a Ϫ58, immediately upstream of the DNA site for CAP) second, promoter-class-specific activating region of (Zhou et al., 1994b; Attey et al., 1994; Belyaeva et al., CAP and the RNA polymerase ␣ subunit N-terminal 1996). Whereas this " anti-inhibition " effect is essential domain. We further show that the two interactions for transcription activation at Class II CAP-dependent affect different steps in transcription initiation. Tran-promoters, it is not the entire basis of transcription acti-scription activation at Class II CAP-dependent pro-vation at Class II CAP-dependent promoters. Thus, re-moters provides a paradigm for understanding how moval of ␣CTD eliminates the requirement for anti-inhi-an activator can make multiple interactions with the bition but does not eliminate transcription activation at transcription machinery, each interaction being re-Class II CAP-dependent promoters (Igarashi et al., 1991; sponsible for a specific mechanistic consequence. Kolb et al., 1993b; West et al., 1993). In a previous report, we have proposed that transcription activation at Class Introduction II CAP-dependent promoters has two components: a first component involving anti-inhibition, mediated by Escherichia coli catabolite activator protein (CAP; also the activating region, and a second component involving referred to as the cAMP receptor protein, CRP) is a direct activation (Zhou et al., 1994b). structurally characterized transcription activator protein In this report, we show that transcription activation (Kolb et al., 1993a). CAP functions by binding, in the at Class II CAP-dependent promoters requires a second, presence …