Interaction with free β′ subunit unmasks DNA‐binding domain of RNA polymerase σ subunit

摘要

>The promoter recognition site on the σ70 initiation factor is shielded from interaction with DNA unless σ70 is bound to the core component of RNA polymerase (RNAP). It is shown that interaction of σ70 with the isolated β′ subunit of Escherichia coli RNAP is sufficient to induce unshielding of the DNA binding site. Using UV-induced DNA-protein cross-linking we demonstrate that free β′ stimulates specific cross-links between region 2 of the σ70 polypeptide and a fragment of the non-template promoter strand containing the TATAAT sequence. Thus the σβ′ subassembly of RNAP can assume a functionally competent conformation independently of the bulk of the RNAP core.