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Conformational switching of Escherichia coli RNA polymerase‐promoter binary complex is facilitated by elongation factor GreA and GreB
Author(s) -
Sen Ranjan,
Nagai Hiroki,
Shimamoto Nobuo
Publication year - 2001
Publication title -
genes to cells
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.912
H-Index - 115
eISSN - 1365-2443
pISSN - 1356-9597
DOI - 10.1046/j.1365-2443.2001.00436.x
Subject(s) - biology , rna polymerase , cleavage (geology) , ternary complex , elongation , escherichia coli , rna , microbiology and biotechnology , biochemistry , enzyme , gene , paleontology , materials science , fracture (geology) , ultimate tensile strength , metallurgy
Background The initiation arrest at a modified λP R promoter is caused by irreversible divergence of the reaction pathway into productive and arrested branches. Escherichia coli GreA and GreB induce cleavage of the nascent transcript and relieve arrest in elongation. They also reduce abortive synthesis at several promoters and relieve initiation arrest. Their mechanism of action during initiation, and its relationship to the branched initiation pathway are unknown. Results The Gre factors mitigated initiation arrest only when they were added to the binary complex of the holoenzyme bound to the λ P R promoter, prior to RNA synthesis. They exerted little effect when they were added to ternary initiation complexes. They accelerated the exchange of the binary complex with its free components by 6–9‐fold. When they are present, a high concentration of the initiating nucleotide increased yield of the full‐length transcript, whereas a low concentration did not. Conclusions All the results presented above can be explained by a model where the productive and arrested pathways diverge at the binary complex stage. The Gre factors relieve the initiation arrest by introducing reversibility between subspecies of the binary complex that are precursors of the two pathways. RNA cleavage is unlikely to cause relief of initiation arrest.