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Cheeran, A. and Suganthan, R.B. and Swapna, G. and Bandey, I. and Achary, M.S. and Nagarajaram, H.A. and Sen, Ranjan (2005) Escherichia coli RNA Polymerase Mutations Located Near the Upstream Edge of an RNA:DNA Hybrid and the Beginning of the RNA-exit Channel are Defective for Transcription Antitermination by the N Protein from Lambdoid Phage H-19B. Journal of Molecular Biology, 352 (1). pp. 28-43. ISSN 0022-2836

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Transcription antitermination is an important mechanism that can control regulation of gene expression. The N protein of lambdoid phages modifies the transcription elongation complex (EC) and helps it to overcome downstream terminators. In this modified EC, the C-terminal domain of N makes specific interactions with RNA polymerase (RNAP). The interacting surface of RNAP for N is unknown. Here, we report five mutations in the β (G1045D) and β′ (P251S, P254L, R270C and G336S) subunits of RNAP that are specifically defective for antitermination by N protein of the lambdoid phage, H-19B. A mutation in the C-terminal domain of N, L108F, suppresses the defect of β′-P254L. Purified mutant holoenzymes exhibit less processive antitermination. The amino acid substitutions in the mutant RNAPs cluster very close to the RNA:DNA hybrid at the beginning of the RNA-exit channel of the EC. We suggest that the action of H-19B N is exerted through the region defined by these amino acids. Wild-type N stabilizes the EC at terminator sites and in this modified EC a part of the terminator hairpin may form but appears to be unstable. We propose that the action of N close to the active center alters the RNAP–nucleic acid interactions around the RNA:DNA hybrid, which impairs proper folding of the terminator hairpin or stabilizes the weak RNA:DNA hybrid, or both.

Item Type: Article
Depositing User: Dr P Divakar
Date Deposited: 21 Jul 2015 09:59
Last Modified: 01 Sep 2017 07:43
URI: http://cdfd.sciencecentral.in/id/eprint/270

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