Molecular mechanism of flucytosine resistance in Candida lusitaniae: contribution of the FCY2, FCY1, and FUR1 genes to 5-fluorouracil and fluconazole cross-resistance.
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ABSTRACT:
SUBMITTER: Papon N
PROVIDER: S-EPMC1797687 | biostudies-literature | 2007 Jan
REPOSITORIES: biostudies-literature
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Molecular mechanism of flucytosine resistance in Candida lusitaniae: contribution of the FCY2, FCY1, and FUR1 genes to 5-fluorouracil and fluconazole cross-resistance.
Papon Nicolas N Noël Thierry T Florent Martine M Gibot-Leclerc Stéphanie S Jean Dorothée D Chastin Christiane C Villard Jean J Chapeland-Leclerc Florence F
Antimicrobial agents and chemotherapy 20061023 1
Inactivation of the FCY2 (cytosine permease), FCY1 (cytosine deaminase), and FUR1 (uracil phosphoribosyltransferase) genes in Candida lusitaniae produced two patterns of resistance to flucytosine. Mutant fur1 demonstrated resistance to 5-fluorouracil, whereas mutants fcy1 and fcy2 demonstrated fluconazole resistance in the presence of subinhibitory flucytosine concentrations. ...[more]
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Project description:The aim of this work was to elucidate the molecular mechanisms of flucytosine (5FC) resistance and 5FC/fluconazole (FLC) cross-resistance in 11 genetically and epidemiologically unrelated clinical isolates of Candida lusitaniae. We first showed that the levels of transcription of the FCY2 gene encoding purine-cytosine permease (PCP) in the isolates were similar to that in the wild-type strain, 6936. Nucleotide sequencing of the FCY2 alleles revealed that 5FC and 5FC/FLC resistance could be correlated with a cytosine-to-thymine substitution at nucleotide 505 in the fcy2 genes of seven clinical isolates, resulting in a nonsense mutation and in a putative nonfunctional truncated PCP of 168 amino acids. Reintroducing a FCY2 wild-type allele at the fcy2 locus of a ura3 auxotrophic strain derived from the clinical isolate CL38 fcy2(C505T) restored levels of susceptibility to antifungals comparable to those of the wild-type strains. In the remaining four isolates, a polymorphic nucleotide was found in FCY1 where the nucleotide substitution T26C resulted in the amino acid replacement M9T in cytosine deaminase. Introducing this mutated allele into a 5FC- and 5FC/FLC-resistant fcy1Delta strain failed to restore antifungal susceptibility, while susceptibility was obtained by introducing a wild-type FCY1 allele. We thus found a correlation between the fcy1 T26C mutation and both 5FC and 5FC/FLC resistances. We demonstrated that only two genetic events occurred in 11 unrelated clinical isolates of C. lusitaniae to support 5FC and 5FC/FLC resistance: either the nonsense mutation C505T in the fcy2 gene or the missense mutation T26C in the fcy1 gene.
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