Control of Transcription Termination

Modulation of Rho-Dependent Transcription Termination in Escherichia coli by the H-NS Family of Proteins

“…The Rho-binding domain in NusG has also recently been shown to interact with the S10 protein subunit of the ribosome, which has implications for the mechanism by which translation-uncoupled nascent transcripts may be subject to termination of their synthesis (9). Although null mutations in rho or nusG confer inviability in wild-type E. coli (11), missense mutations in the two genes are known that confer a transcription termination-defective (that is, polarity relief) phenotype (1,12,13,27,36).In the present study, we found that overexpression of the protein YdgT restores transcriptional polarity in the rho and nusG mutants and, furthermore, that the combination of rho, ydgT, and hha mutations confers extreme sickness in E. coli. YdgT (also called Cnu [30]) and Hha belong to the H-NS family of proteins (33), whose prototypic member H-NS participates in both regulation of transcription initiation and nucleoid structure (reviewed in references 16, 20, 23, and 59).…”

“…Finally, the polarity defects of rho and nusG mutants were exacerbated by Hha and YdgT deficiency. A model is proposed that invokes a novel role for the polymeric architectural scaffold formed on DNA by H-NS and StpA independent of the gene-silencing functions of these nucleoid proteins, in modulating Rho-dependent transcription termination such that interruption of the scaffold (as obtained by expression either of the H-NS oligomerization variants or of YdgT) is associated with improved termination efficiency in the rho and nusG mutants.Translation is a cotranscriptional process in both eubacteria and archaebacteria (1,9,25,45,50), and it has been proposed that such coupling is a defining characteristic of prokaryotic life (34, 64). The maintenance of transcription-translation coupling in a prokaryotic cell would require dynamic inter-regulation between the binding and progression of a pioneer ribosome on the nascent transcript on the one hand and the rate of transcription elongation on the other (9, 45); however, the detailed mechanisms by which such regulation is achieved are not known.…”

“…The maintenance of transcription-translation coupling in a prokaryotic cell would require dynamic inter-regulation between the binding and progression of a pioneer ribosome on the nascent transcript on the one hand and the rate of transcription elongation on the other (9, 45); however, the detailed mechanisms by which such regulation is achieved are not known. Furthermore, in bacteria such as Escherichia coli, nascent transcripts that are not simultaneously translated are subject to a mechanism of factor-dependent transcription termination (also referred to as transcriptional polarity) (reviewed in references 1, 6, 15, 40, 44, 47, and 52), so that the occurrence of translation-uncoupled transcription is minimized within the cells (11, 43).Factor-dependent (also called Rho-dependent) transcription termination is mediated by, among others, the Rho and NusG proteins (1,6,15,39,40,44,47,52). Although the structures of the two proteins have been determined and several of their biochemical properties have been characterized, the precise mechanisms of their action in transcription termination remain unclear, even controversial.…”

Compromised Factor-Dependent Transcription Termination in a nusA Mutant of Escherichia coli: Spectrum of Termination Efficiencies Generated by Perturbations of Rho, NusG, NusA, and H-NS Family Proteins

“…The mechanism is absolutely dependent on the essential Rho protein that binds the nascent transcript and is then believed to signal RNA polymerase to terminate transcription, but there is no consensus as yet on its details (reviewed in references 1,3,14,40,41,43, and 48; see also references 21 and 31). As with their effects on transcription elongation, NusA and NusG have been reported to function antagonistically for Rho-dependent transcription termination as well, with NusG increasing its efficiency (7,8,11,29,35,38,52) and NusA decreasing it (8,27,(32)(33)(34); indeed, it has been reported that mutations in rho can suppress the inviability associated with the loss of NusA (58).…”

Preferential interaction of the his pause RNA hairpin with RNA polymerase β subunit residues 904–950 correlates with strong transcriptional pausing

“…10) and can trigger pausing or termination by RNA polymerase II in vitro (11). Although RNA hairpin-RNA polymerase interactions have long been suggested to play roles in pausing (12), termination (13)(14)(15), and antitermination (16), no direct evidence for these interactions or their effects exists.…”