H3K4 methylation regulates development, DNA repair, and virulence in Mucorales
Authors: Osorio-Concepción Macario , Lax Carlos , Lorenzo-Gutiérrez Damaris , Cánovas-Márquez José Tomás , Tahiri Ghizlane , Navarro Eusebio , Binder Ulrike , Nicolás Francisco Esteban , Garre Victoriano 
Published: June 2023

Mucorales are basal fungi that opportunistically cause a fatal infection known as mucormycosis (black fungus disease), which poses a significant threat to human health due to its high mortality rate and its recent association with SARS-CoV-2 infections. On the other hand, histone methylation is a regulatory mechanism with pleiotropic effects, including the virulence of several pathogenic organisms. However, the role of epigenetic changes at the histone level never has been studied in Mucorales. Here, we dissected the functional role of Set1, a histone methyltransferase that catalyzes the methylation of H3K4, which is associated with the activation of gene transcription and virulence. A comparative analysis of theMucor lusitanicusgenome (previously known asMucor circinelloidesf.lusitanicus) identified only one homolog of Set1 fromCandida albicansandSaccharomyces cerevisiaethat contains the typical SET domain. Knockout strains in the geneset1lacked H3K4 monomethylation, dimethylation, and trimethylation enzymatic activities. These strains also showed a significant reduction in vegetative growth and sporulation. Additionally,set1null strains were more sensitive to SDS, EMS, and UV light, indicating severe impairment in the repair process of the cell wall and DNA lesions and a correlation between Set1 and these processes. During pathogen-host interactions, strains lacking theset1gene exhibited shortened polar growth within the phagosome and attenuated virulence bothin vitroandin vivo. Our findings suggest that the histone methyltransferase Set1 coordinates several cell processes related to the pathogenesis ofM. lusitanicusand may be an important target for future therapeutic strategies against mucormycosis.

Author Summary

The knowledge regarding the role of epigenetic modification in regulating gene expression in early diverging fungi is scarce, despite they represent an important fraction of the fungal kingdom. The order Mucorales, which causes the lethal infection known as mucormycosis, is not an exception. There is an urgent need to enhance our understanding of the biology of these fungi to develop effective treatments for mucormycosis, which are currently absent due to the natural resistance of Mucorales to most antifungal drugs. This work represents the first investigation into the role of the methylation of lysine 4 on histone 3 (H3K4) in a mucoralean fungus. This was accomplished by the generation of deletion mutants in theset1gene, which encodes the specific H3K4 methyltransferase. Phenotypic analyses of these mutants suggest that H3K4 methylation regulates physiology, development, cell wall integrity, and DNA repair. Furthermore, our findings indicate that it also contributes to the virulence ofM. lusitanicus, as strains lacking theset1gene exhibited shortened polar growth within the phagosome and attenuated virulence bothin vitroandin vivo.