Transcriptome analysis of Sch9-depedent thermotolerance mechanism reveals a dual functional heat shock transcription factor, Hsf1, in Cryptococcus neoformans [HSF1 overexpression]

ABSTRACT: Thermotolerance is a crucial virulence attribute for Cryptococcus neoformans, which causes fatal fungal meningitis in humans. A protein kinase, Sch9, suppresses the thermotolerance of C. neoformans but its regulatory mechanism remains unknown. Here we elucidated the Sch9-dependent and -independent signaling networks for modulating the thermotolerance of C. neoformans through a genome-wide transcriptome analysis and reverse genetics approaches. We found that more than 1,800 genes were under transcriptional control during temperature upshift. Genes encoding for molecular chaperones and heat shock proteins were mainly upregulated, while those for translation, transcription, and sterol biosynthesis were highly suppressed. In this process Sch9 was found to regulate basal or induced expression levels of some temperature-responsive genes. Interestingly we found that Sch9 was involved in transcriptional regulation of the Ire1 kinase, which is a key sensor for the unfolded protein response pathway, and was found to be involved in ER stress response. Most notably, our data demonstrated that expression of HSF1, encoding a heat shock transcription factor 1, was downregulated during temperature upshift and Sch9 suppresses its downregulation. In spite of such expression patterns, Hsf1 was essential for growth and its overexpression indeed promoted the thermotolerance of C. neoformans, suggesting dual roles of Hsf1 in thermotolerance. This idea was supported by additional transcriptome analysis with HSF1 overexpression strain, which revealed that Hsf1 served as both activator and repressor. Hsf1 promoted genes such as Hsp104 and Hsp70 (Ssa1 and Ssa2), both of which were found to be highly upregulated during temperature upshift and required for thermotolerance, while Hsf1 repressed genes involved in oxidative stress and thermotolerance.

ORGANISM(S): Cryptococcus neoformans var. grubii Cryptococcus neoformans var. neoformans JEC21

PROVIDER: GSE66509 | GEO | 2015/06/01

SECONDARY ACCESSION(S): PRJNA277182

REPOSITORIES: GEO