Recycling of Ribosomal Complexes Stalled at the Step of Elongation in Escherichia coli

Singh, Nongmaithem Sadananda and Ahmad, Rais and Sangeetha, Ramachandran and Varshney, Umesh (2008) Recycling of Ribosomal Complexes Stalled at the Step of Elongation in Escherichia coli. In: Journal of Molecular Biology, 380 (3). pp. 451-464.

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Abstract

Translating ribosomes often stall during elongation. The stalled ribosomes are known to be recycled by tmRNA (SsrA)-mediated trans-translation.Another process that recycles the stalled ribosomes is characterized by peptidyl-tRNA release. However, the mechanism of peptidyl-tRNA release from the stalled ribosomes is not well understood.We used a defined system of an AGA-minigene containing a small open reading frame (ATG AGA AGA). Translation of the AGA- inigene mRNA is toxic to Escherichia coli because it stalls ribosomes during elongation and sequesters $tRNA^{Arg4}$ as a short-chain peptidyl-$tRNA^{Arg4}$ in the ribosomal P-site. We show that a ribosome recycling factor (RRF)-mediated process rescues the host from the AGA-minigene toxicity by releasing the peptidyl-$tRNA^{Arg4}$ from the ribosomes. The growth phenotypes of E. coli strains harboring mutant alleles of RRF and initiation factor 3 (IF3) genes and their consequences on \lambda immP22 phage replication upon AGA-minigene expression reveal that IF3 facilitates the RRF-mediated processing of the stalled ribosomes. Additionally, we have designed a uracil DNA glycosylase gene construct, ung-stopless, whose expression is toxic to E. coli. We show that the RRF-mediated process also alleviates the ung-stopless construct-mediated toxicity to the host by releasing the ung mRNA from the ribosomes harboring long-chain peptidyl-tRNAs.

Item Type:	Journal Article
Publication:	Journal of Molecular Biology
Publisher:	Elsevier
Additional Information:	Copyright of this article belongst to Elsevier.
Keywords:	RRF;peptidyl-tRNA;ssrA;minigene;Ung.
Department/Centre:	Division of Biological Sciences > Microbiology & Cell Biology
Date Deposited:	06 Aug 2008
Last Modified:	19 Sep 2010 04:48
URI:	http://eprints.iisc.ac.in/id/eprint/15469

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