Deciphering the functions of Spt20 in the SAGA complex: Implications for Cryptococcus neoformans virulence

Abstract

Aims

The SAGA complex is a conserved transcriptional co-activator essential for eukaryotic gene regulation. In fungi of the Ascomycota, the core protein Spt20 contributes to the structure and function of SAGA. This study aimed to identify and characterize SPT20 in Cryptococcus neoformans, the WHO top-ranked critical priority group species on their Fungal Priority Pathogen list.

Materials and methods

Identification of C. neoformans SPT20 revealed the presence of a tRNA gene within its 5′ UTR. Precisely deleting the SPT20 ORF preserved the tRNA gene while enabling analysis of Spt20 function. Phenotypic assays assessed growth under stress, capsule formation, and antifungal susceptibility. RT-qPCR divulged effects on transcriptional regulation of SAGA components, while Western blotting evaluated changes in histone acetylation and deubiquitination. A murine inhalation model assessed virulence.

Key findings

Loss of SPT20 impaired growth under a number of stresses, influenced capsule formation, increased antifungal susceptibility, and disrupted expression of most genes encoding SAGA complex proteins. The mutant exhibited defects in several histone modifications as well as severely compromised virulence in mice.

Significance

Characterization of SPT20 in C. neoformans has provided important insights into the role of this protein as a critical regulator of survival and virulence in this clinically important species.