Summary auto-generated
This study reports the cloning and characterization of the topoisomerase I gene (TOP1) from Candida albicans, a major human fungal pathogen. Using PCR and genomic library screening, researchers isolated and sequenced the TOP1 gene, finding its predicted protein shares 58.8% identity with Saccharomyces cerevisiae topoisomerase I. A conditional gene disruption strain was constructed where one TOP1 copy was deleted and the other placed under a maltose-inducible, glucose-repressible promoter. When the promoter was repressed, cells exhibited slow growth and abnormal morphology, indicating TOP1 is not essential but important for normal physiology. Virulence testing in a mouse infection model showed markedly reduced pathogenicity in the conditional strain and slight attenuation in a single knockout strain, suggesting TOP1 plays a dose-dependent role in C. albicans infection. Despite reduced virulence, pathogenic cells were still recoverable from infected kidneys up to 22 days post-infection, demonstrating persistent infection capability even with compromised topoisomerase I function.
Key findings
- C. albicans TOP1 gene encodes a topoisomerase I protein with 58.8% identity to S. cerevisiae topoisomerase I and contains conserved catalytic domains
- TOP1 is not essential for cell growth but depletion causes slow growth and abnormal cell morphology
- Deletion or conditional repression of TOP1 reduces virulence in a mouse infection model in a dose-dependent manner
- Viable C. albicans cells persist in infected kidneys up to 22 days post-infection despite reduced TOP1 expression
This summary was generated automatically from the article PDF and is not part of the original publication. Refer to the PDF for the authoritative text.
Abstract
We report here the cloning of the Candida albicans genomic topoisomerase I gene (TOP1) by use of PCR and subsequent hybridization. The predicted protein sequence shared 58.8% identity with the Saccharomyces cerevisiae topoisomerase I and 30-50% identity with other eukaryotic topoisomerase I proteins. A conditional gene disruption strain (CWJ477) was constructed so that one copy of TOP1 was deleted and the other copy of TOP1 was placed under a regulatable promoter. Under repressed conditions, cells grew slowly and cell morphology was abnormal. The virulence of CWJ477 was markedly reduced in a mouse model system, and that of the single gene knockout-strain was slightly attenuated, indicating that TOP1 might play a role in the infection of C. albicans in mice in a dose-dependent manner. Despite the reduced virulence of both the single and double knockout strains, viable cells of the pathogen were recovered from the kidneys as late as 22 d post- infection.