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The ribosome binding site of a mini‐ ORF protects a T3SS mRNA from degradation by RNase E
Author(s) -
Lodato Patricia B.,
Hsieh PingKun,
Belasco Joel G.,
Kaper James B.
Publication year - 2012
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/mmi.12050
Subject(s) - biology , rnase p , translocon , ribosome , messenger rna , translation (biology) , start codon , stop codon , ribonuclease iii , microbiology and biotechnology , open reading frame , gene , rna , genetics , peptide sequence , rna interference , chromosomal translocation
Summary Enterohaemorrhagic E scherichia coli harbours a pathogenicity island encoding a type 3 secretion system used to translocate effector proteins into the cytosol of intestinal epithelial cells and subvert their function. The structural proteins of the translocon are encoded in a major espADB mRNA processed from a precursor. The translocon mRNA should be highly susceptible to RNase E cleavage because of its AU ‐rich leader region and monophosphorylated 5′‐terminus, yet it manages to avoid rapid degradation. Here, we report that the espADB leader region contains a strong S hine– D algarno element ( SD 2) and a translatable mini‐ ORF of six codons. Disruption of SD 2 so as to weaken ribosome binding significantly reduces the concentration and stability of esp mRNA , whereas codon substitutions that impair translation of the mini‐ ORF have no such effect. These findings suggest that occupancy of SD 2 by ribosomes, but not mini‐ ORF translation, helps to protect espADB mRNA from degradation, likely by hindering RNase E access to the AU ‐rich leader region.