Background: The transcriptional activator Pdr1 has been implicated in C. glabrata azole and multidrug resistance (MDR). In S. cerevisiae, histone modifications also affect drug susceptibility and MDR gene expression and recent data suggest a role for histone modifying enzymes (HME) in C. glabrata fluconazole sensitivity. Methods: C. glabrata HME deletion strains were constructed by PCR product-based gene disruption. Susceptibilities were determined by broth microdilution assays. RNA levels were analyzed by slot-blot hybridization with gene specific probes. Results: Using the C. glabrata genome database, we were able to identify several putative HME based on similarity to known S. cerevisiae proteins. C. glabrata genes for several putative HME genes were deleted and the resulting strains tested for altered drug sensitivity. Of these, the loss of CgGCN5 (histone acetyltransferase homolog) resulted in the strongest phenotype with 32- and 64-fold increases in susceptibility to fluconazole and miconazole, respectively. These changes in azole sensitivity were within 2- to 4-fold of the changes observed in strains deleted in the MDR transcription factor CgPDR1; however, this was drug-dependent. In particular, the CgPDR1 disruptants display up to 64-fold increased in cycloheximide susceptibility while the Cggcn5916; mutants show little change (no more than 2- to 4-fold hypersensitive). RNA hybridization analysis revealed that the loss of Gcn5 resulted in decreased expression of CgCDR1 (2- to 3-fold) and but more significantly CgPDH1 (4- to >10-fold) which encode for the major MDR-associated efflux pumps in C. glabrata. In contrast, both CgCDR1 and CgPDH1 were decreased >10-fold with the loss of Pdr1, which may explain the differences in drug sensitivity between strains. Conclusions: Our data suggests that C. glabrata HME are important for azole drug resistance by modulating MDR gene expression. We also show that Pdr1-mediated resistance to other drugs may be HME-independent.
Full conference title:
46th Interscience Conference on Antimicrobial Agents and Chemotherapy
- ICAAC 46th