Heterozygosity and functional allelic variation in the Candida albicans efflux pump genes CDR1 and CDR2
| Autor: | Richard D. Cannon, Barbara R. Holland, Brian C. Monk, Soo-Wee Ong, Sarah Tsao, Aki Kaneko, Jan Schmid, Erwin Lamping, Kyoko Niimi, Ann R. Holmes, Masakazu Niimi |
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| Rok vydání: | 2006 |
| Předmět: |
Azoles
Heterozygote Antifungal Agents Sequence analysis Blotting Western Molecular Sequence Data Locus (genetics) Microbial Sensitivity Tests Biology Microbiology Fungal Proteins Loss of heterozygosity Negative selection Drug Resistance Fungal Gene Expression Regulation Fungal Candida albicans Cloning Molecular Allele DNA Fungal Fluconazole Molecular Biology Gene Alleles Genetics Reverse Transcriptase Polymerase Chain Reaction Fungal genetics Genetic Variation Membrane Transport Proteins Sequence Analysis DNA biology.organism_classification Drug Resistance Multiple Mutagenesis Site-Directed ATP-Binding Cassette Transporters |
| Zdroj: | Molecular Microbiology. 62:170-186 |
| ISSN: | 1365-2958 0950-382X |
| DOI: | 10.1111/j.1365-2958.2006.05357.x |
| Popis: | Summary Elevated expression of the plasma membrane drug efflux pump proteins Cdr1p and Cdr2p was shown to accompany decreased azole susceptibility in Candida albicans clinical isolates. DNA sequence analysis revealed extensive allelic heterozygosity, particularly of CDR2. Cdr2p alleles showed different abilities to transport azoles when individually expressed in Saccharomyces cerevisiae. Loss of heterozygosity, however, did not accompany decreased azole sensitivity in isogenic clinical iso- lates. Two adjacent non-synonymous single nucle- otide polymorphisms (NS-SNPs), G1473A and I1474V in the putative transmembrane (TM) helix 12 of CDR2, were found to be present in six strains including two isogenic pairs. Site-directed mutagen- esis showed that the TM-12 NS-SNPs, and princi- pally the G1473A NS-SNP, contributed to functional differences between the proteins encoded by the two Cdr2p alleles in a single strain. Allele-specific PCR revealed that both alleles were equally frequent among 69 clinical isolates and that the majority of isolates (81%) were heterozygous at the G1473A/ I1474V locus, a significant (P 0.001) deviation from the Hardy-Weinberg equilibrium. Phylogenetic analysis by maximum likelihood (Paml) identified 33 codons in CDR2 in which amino acid allelic changes showed a high probability of being selectively advantageous. In contrast, all codons in CDR1 were under purifying selection. Collectively, these results indicate that possession of two functionally different CDR2 alleles in individual strains may confer a selective advantage, but that this is not necessarily due to azole resistance. |
| Databáze: | OpenAIRE |
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