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- Babina, Arianne M., et al.
(författare)
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Suppression of the Escherichia coli rnpA49 conditionally lethal phenotype by different compensatory mutations
- 2024
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Ingår i: RNA. - : Cold Spring Harbor Laboratory Press (CSHL). - 1355-8382 .- 1469-9001. ; 30:8, s. 977-991
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Tidskriftsartikel (refereegranskat)abstract
- RNase P is an essential enzyme found across all domains of life that is responsible for the 5 '-end maturation of precursor tRNAs. For decades, numerous studies have sought to elucidate the mechanisms and biochemistry governing RNase P function. However, much remains unknown about the regulation of RNase P expression, the turnover and degradation of the enzyme, and the mechanisms underlying the phenotypes and complementation of specific RNase P mutations, especially in the model bacterium, Escherichia coli. In E. coli, the temperature-sensitive (ts) rnpA49 mutation in the protein subunit of RNase P has arguably been one of the most well-studied mutations for examining the enzyme's activity in vivo. Here, we report for the first time naturally occurring temperature-resistant suppressor mutations of E. coli strains carrying the rnpA49 allele. We find that rnpA49 strains can partially compensate the ts defect via gene amplifications of either RNase P subunit (rnpA49 or rnpβ) or by the acquisition of loss-of-function mutations in Lon protease or RNase R. Our results agree with previous plasmid overexpression and gene deletion complementation studies, and importantly suggest the involvement of Lon protease in the degradation and/or regulatory pathway(s) of the mutant protein subunit of RNase P. This work offers novel insights into the behavior and complementation of the rnpA49 allele in vivo and provides direction for follow-up studies regarding RNase P regulation and turnover in E. coli.
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| 2. |
- Freihofer, Pietro, et al.
(författare)
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Nonmutational compensation of the fitness cost of antibiotic resistance in mycobacteria by overexpression of tlyA rRNA methylase
- 2016
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Ingår i: RNA. - : Cold Spring Harbor Laboratory. - 1355-8382 .- 1469-9001. ; 22:12, s. 1836-1843
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Tidskriftsartikel (refereegranskat)abstract
- Several studies over the last few decades have shown that antibiotic resistance mechanisms frequently confer a fitness cost and that these costs can be genetically ameliorated by intra- or extragenic second-site mutations, often without loss of resistance. Another, much less studied potential mechanism by which the fitness cost of antibiotic resistance could be reduced is via a regulatory response where the deleterious effect of the resistance mechanism is lowered by a physiological alteration that buffers the mutational effect. In mycobacteria, resistance to the clinically used tuberactinomycin antibiotic capreomycin involves loss-of-function mutations in rRNA methylase TIyA or point mutations in 16S rRNA (in particular the A1408G mutation). Both of these alterations result in resistance by reducing drug binding to the ribosome. Here we show that alterations of tlyA gene expression affect both antibiotic drug susceptibility and fitness cost of drug resistance. In particular, we demonstrate that the common resistance mutation A1408G is accompanied by a physiological change that involves increased expression of the tlyA gene. This gene encodes an enzyme that methylates neighboring 16S rRNA position C1409, and as a result of increased TIyA expression the fitness cost of the A1408G mutation is significantly reduced. Our findings suggest that in mycobacteria, a nonmutational mechanism (i.e., gene regulatory) can restore fitness to genetically resistant bacteria. Our results also point to a new and clinically relevant treatment strategy to combat evolution of resistance in multidrug-resistant tuberculosis. Thus, by utilizing antagonistic antibiotic interactions, resistance evolution could be reduced.
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