부산대학교 도서관

ABSTRACTThe virulence of Candida albicansmutants lacking one or both copies of RAD52, a gene involved in homologous recombination (HR), was evaluated in a murine model of hematogenously disseminated candidiasis. In this study, the virulence of the rad52Δ mutant was dependent upon the inoculum concentration. Mice survived at a cell inoculum of 1 × 106, but there was a decrease in survival time at dosages of 1.5 × 106and especially at 3 × 106cells per animal. The heterozygote RAD52/rad52behaved like wild type, whereas a reintegrant strain was intermediate in its ability to cause death compared to these strains and to the avirulent rad52/rad52null at inocula of 1 × 106and 1.5 × 106cells. A double mutant, lig4/lig4/rad52/rad52, was avirulent at all inocula used. PCR analysis of the RAD52and/or LIG4loci showed that all strains recovered from animals matched the genotype of the inoculated strains. Analysis of the electrophoretical karyotypes indicated that the inoculated, reintegrant strain carried a large deletion in one copy of chromosome 6 (the shortest homologue, or Chr6b). Interestingly, truncated Chr6b was regenerated in all the strains recovered from moribund animals using the homologue as a template. Further, regeneration of Chr6b was paralleled by an increase in virulence that was still lower than that of wild type, likely because of the persistent loss of heterozygosity in the regenerated region. Overall, our results indicate that systemic candidiasis can develop in the absence of HR, but simultaneous elimination of both recombination pathways, HR and nonhomologous end-joining, suppresses virulence even at very high inocula.