Analysis of Cyp51 protein sequences shows 4 major Cyp51 gene family groups across Fungi

Abstract

Azole drugs target fungal sterol biosynthesis and are used to treat millions of human fungal infections each year. Resistance to azole drugs has emerged in multiple fungal pathogens including Candida albicans, Cryptococcus neoformans, Histoplasma capsulatum, and Aspergillus fumigatus. The most well-studied resistance mechanism in A. fumigatus arises from missense mutations in the coding sequence combined with a tandem repeat in the promoter of cyp51A, which encodes a cytochrome P450 enzyme in the fungal sterol biosynthesis pathway. Filamentous members of Ascomycota such as A. fumigatus have either one or two of three Cyp51 paralogs (Cyp51A, Cyp51B, and Cyp51C). Most previous research in A. fumigatus has focused on Cyp51A due to its role in azole resistance. We used the A. fumigatus Cyp51A protein sequence as the query in database searches to identify Cyp51 proteins across Fungi. We found 435 Cyp51 proteins in 301 species spanning from early-diverging fungi (Blastocladiomycota, Chytridiomycota, Zoopagomycota and Mucormycota) to late-diverging fungi (Ascomycota and Basidiomycota). We found these sequences formed 4 major Cyp51 groups: Cyp51, Cyp51A, Cyp51B, and Cyp51C. Surprisingly, we found all filamentous Ascomycota had a Cyp51B paralog, while only 50% had a Cyp51A paralog. We created maximum likelihood trees to investigate the evolution of Cyp51 in Fungi. Our results suggest Cyp51 is present in all fungi with three paralogs emerging in Pezizomycotina, including Cyp51C which appears to have diverged from the progenitor of the Cyp51A and Cyp51B groups. Author SummaryEach year millions of people are infected by a fungal pathogen and receive antifungal treatment with azole drugs. Resistance to azole drugs is becoming increasingly prevalent and is mostly caused by mutations in the azole drug target, Cyp51. Aspergillus fumigatus is an airborne fungal pathogen that causes more than 600,000 deaths every year. Azole resistance in A. fumigatus is primarily driven by a promoter repeat coupled with mutations in cyp51A. In our study, we found 435 Cyp51 proteins in 4 major groups across Fungi, with some species having multiple Cyp51 proteins (Cyp51, Cyp51A, Cyp51B, and Cyp51C). Although most research in A. fumigatus has focused on Cyp51A, we found Cyp51B in all filamentous Ascomycota fungi showing it is more conserved than Cyp51A and likely plays a vital role in these fungi. Author Summary (Shortened)Resistance to azole drugs is becoming increasingly prevalent and is mostly caused by mutations in the azole drug target, Cyp51. Azole resistance in Aspergillus fumigatus is primarily driven by a promoter repeat coupled with mutations in cyp51A. We found 435 Cyp51 proteins in 4 major groups across Fungi, with some species having multiple Cyp51 proteins (Cyp51, Cyp51A, Cyp51B, and Cyp51C). Although most research focuses on Cyp51A, we found Cyp51B in all filamentous Ascomycota fungi showing its more conserved than Cyp51A.