Forskning ved Københavns Universitet - Københavns Universitet


A small RNA controls expression of the chitinase ChiA in Listeria monocytogenes

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  • A Small...

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  • Jesper S Nielsen
  • Larsen, Marianne Halberg
  • Eva Maria Sternkopf Lillebæk
  • Teresa M. Bergholz
  • Mie H.G. Christiansen
  • Kathryn J. Boor
  • Martin Wiedmann
  • Birgitte H. Kallipolitis
In recent years, more than 60 small RNAs (sRNAs) have been identified in the gram-positive human pathogen Listeria
monocytogenes, but their putative roles and mechanisms of action remain largely unknown. The sRNA LhrA was recently
shown to be a post-transcriptional regulator of a single gene, lmo0850, which encodes a small protein of unknown function.
LhrA controls the translation and degradation of the lmo0850 mRNA by an antisense mechanism, and it depends on the
RNA chaperone Hfq for efficient binding to its target. In the present study, we sought to gain more insight into the
functional role of LhrA in L. monocytogenes. To this end, we determined the effects of LhrA on global-wide gene expression.
We observed that nearly 300 genes in L. monocytogenes are either positively or negatively affected by LhrA. Among these
genes, we identified lmo0302 and chiA as direct targets of LhrA, thus establishing LhrA as a multiple target regulator.
Lmo0302 encodes a hypothetical protein with no known function, whereas chiA encodes one of two chitinases present in L.
monocytogenes. We show here that LhrA acts as a post-transcriptional regulator of lmo0302 and chiA by interfering with
ribosome recruitment, and we provide evidence that both LhrA and Hfq act to down-regulate the expression of lmo0302
and chiA. Furthermore, in vitro binding experiments show that Hfq stimulates the base pairing of LhrA to chiA mRNA. Finally,
we demonstrate that LhrA has a negative effect on the chitinolytic activity of L. monocytogenes. In marked contrast to this,
we found that Hfq has a stimulating effect on the chitinolytic activity, suggesting that Hfq plays multiple roles in the
complex regulatory pathways controlling the chitinases of L. monocytogenes.
TidsskriftP L o S One
Udgave nummer4
Antal sider11
StatusUdgivet - 2011

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