We have studied the specificity and kinetics of release of nascent RNA from ternary transcription complexes by Escherichia coli transcription termination factor rho in vitro. Stable ternary complexes, initiated at the λ P(R) promoter, were prepared either by quenching the elongation reaction with EDTA or by preventing further elongation by incorporating 3'-O-methyl nucleotides at the 3' end of the nascent RNA chains. We find that rho protein can only release λ P(R)-initiated transcripts from ternary complexes in which transcription has proceeded beyond 288 base pairs from P(R); shorter chains are not released. Substitution of inosine for guanosine in the nascent RNA permits the rho-dependent release process to operate on complexes located as close as 108-116 base pairs downstream from P(R). The regions of the template from which rho can release transcripts correspond, for both guanosine- and inosine-containing RNA, to those within which rho-dependent termination has also been shown to occur (Morgan, W.D., Bear, D.G., and von Hippel, P.H. (1983) J. Biol. Chem. 258, 9553-9564, 9565-9574). The half-time for the major part of the release process is less than 10 s. These results are in good accord with the hypothesis that the specificity of rho-dependent termination is jointly determined by two separable processes: (i) the specificity of rho binding to the nascent RNA chain and (ii) the location and strength of RNA polymerase-pausing sites.
|Original language||English (US)|
|Number of pages||8|
|Journal||Journal of Biological Chemistry|
|State||Published - 1984|
ASJC Scopus subject areas
- Molecular Biology
- Cell Biology