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jueves, 15 de marzo de 2018

Nuevo sistema TA en Corynebacterium glutamicum

Glutamine-rich toxic proteins GrtA, GrtB, and GrtC together with the antisense RNA AsgR constitute a toxin–antitoxin-like system in Corynebacterium glutamicum.

The Corynebacterium glutamicum R grtA (cgR_2936), grtB (cgR_2934), and grtC (cgR_2933) genes were identified as paralogs encoding glutamine-rich toxic proteins. We also identified a new antisense small RNA AsgR (antisense sRNA for grtA) that overlaps the 3′ end of the grtA gene. Single over-expressions of grtA, grtB, and grtC resulted in complete inhibition of Escherichia coli cell growth. This growth was rescued by co-expression of AsgR. Similar effects were observed in C. glutamicum, although the toxicities of these proteins were moderate. Inhibition of AsgR transcription resulted in increased levels and prolonged half-lives of grtA, grtB, and grtC mRNAs. We also found that the expression levels of grtA, grtB, and grtC were increased in an RNase III deletion mutant. Primer extension analysis revealed the RNase III cleavage site to be in the 3′ untranslated region (3′-UTR) of the grtA mRNA. The expression levels of grtA, grtB, and grtC were increased after exposure to several stresses, including heat shock, treatment with penicillin G, lysozyme, or H2O2. The deletions of grtABC and asgR genes resulted in decreased survival rate under several stresses. These results indicate that GrtABC and AsgR constitute a type I toxin–antitoxin-like system in C. glutamicum.


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