E. coli 6S RNA release from RNA polymerase requires σ⁷⁰ ejection by scrunching and is orchestrated by a conserved RNA hairpin

pRNA is present in the S3 and S4 states of the 6S RNA release complex. (A, lanes 1–4) Time course using ³²P radiolabeled AU (*pAU) dinucleotide, time points 2, 5, 10, and 30 min. (A, lanes 6–9) ³²P body-labeled 6S RNA (6S*) showing bound (S2) complex followed by the emergence of the S3 and S4 states after addition of 25 μM AU, 147 μM of each CTP, GTP, and UTP. B indicates bound Eσ⁷⁰ complex (lane 5). (B) Size characterization of *pAU-labeled pRNA extracted from the S3 and S4 states. Recovered RNA was analyzed using 23% denaturing PAGE. S4 H indicates alkaline hydrolysis ladder of the S4 state pRNA.