Toc1, Toc2, and Skn7 null mutants treated with Flucytosine

A family of APSES transcription factor is known to be fungal-specific transcriptional regulators and play important roles in governing growth, differentiation, and virulence of diverse fungal pathogens. Yet none of APSES-like transcription factors have been identified and investigated in a basidiomycetous fungal pathogen, Cryptococcus neoformans. In the present study we discovered an APSES-like transcription factor, Msa1 (Mbp1/Swi4-like APSES protein 1), as one of novel flucytosine-responsive genes (total 194 genes) identified through comparative transcriptome analysis of C. neoformans hybrid sensor kinase mutants, tco1 and tco2 mutants, which displayed differential flucytosine-susceptibility. Supporting the microarray data, Northern blot and quantitative RT-PCR analysis confirmed that expression of MSA1 is rapidly induced in response to flucytosine in the wild-type strain, but not in the tco1 and tco2 mutants. Furthermore, C. neoformans with deletion of the MSA1 gene exhibited increased susceptibility to flucytosine. Intriguingly, Msa1 plays pleiotropic roles in diverse cellular process of C. neoformans. Msa1 positively regulates ergosterol biosynthesis and thereby its inhibition confers increased susceptibility and resistance to amphotericin B and azole drugs, respectively. Msa1 is also involved in DNA damage repair counteracting genotoxic stresses. During sexual differentiation Msa1 represses pheromone production, but promotes cell-cell fusion. Furthermore Msa1 is required for production of antioxidant melanin pigment and full virulence of C. neoformans. Finally we also performed DNA microarrray analysis to identify Msa1-regulated genes in C. neoformans. A majority of them were found to be involved in cell cycle regulation and DNA repair. Therefore, this study provides a novel antifungal therapeutic method for treatment of cryptococcosis. There are more than 95% of genome homology between JEC21 and H99. Therefore 24 slides of JEC21 (cryptococcus neoformans var. neoformans serotype D) 70-mer oligo are used in this analysis, 3 biological replicate experiments are performed, total RNAs are extracted under 2 conditions (with or without treatment of Flucytosine) with 4 strains from H99 (H99 Wild type strain (Cryptococcus neoformans var. grubii serotype A), tco1Δ , tco2Δ , skn7Δ), We use the mixed all of total RNAs from this experiment as a control RNA. We use Cy5 as Sample dye and Cy3 as a control dye.