Post-transcriptional regulation of the Sef1 transcription factor controls the virulence of Candida albicans in its mammalian host

PLoS Pathog. 2012;8(11):e1002956. doi: 10.1371/journal.ppat.1002956. Epub 2012 Nov 1.

Abstract

The yeast Candida albicans transitions between distinct lifestyles as a normal component of the human gastrointestinal microbiome and the most common agent of disseminated fungal disease. We previously identified Sef1 as a novel Cys(6)Zn(2) DNA binding protein that plays an essential role in C. albicans virulence by activating the transcription of iron uptake genes in iron-poor environments such as the host bloodstream and internal organs. Conversely, in the iron-replete gastrointestinal tract, persistence as a commensal requires the transcriptional repressor Sfu1, which represses SEF1 and genes for iron uptake. Here, we describe an unexpected, transcription-independent role for Sfu1 in the direct inhibition of Sef1 function through protein complex formation and localization in the cytoplasm, where Sef1 is destabilized. Under iron-limiting conditions, Sef1 forms an alternative complex with the putative kinase, Ssn3, resulting in its phosphorylation, nuclear localization, and transcriptional activity. Analysis of sfu1 and ssn3 mutants in a mammalian model of disseminated candidiasis indicates that these post-transcriptional regulatory mechanisms serve as a means for precise titration of C. albicans virulence.

MeSH terms

  • Candida albicans / genetics
  • Candida albicans / metabolism*
  • Candida albicans / pathogenicity*
  • Candidiasis / genetics
  • Candidiasis / metabolism
  • Core Binding Factor Alpha 1 Subunit / biosynthesis*
  • Core Binding Factor Alpha 1 Subunit / genetics
  • Cyclin-Dependent Kinases / genetics
  • Cyclin-Dependent Kinases / metabolism
  • Fungal Proteins / genetics
  • Fungal Proteins / metabolism*
  • Gene Expression Regulation, Fungal / physiology*
  • Humans
  • Iron / metabolism
  • Multiprotein Complexes / genetics
  • Multiprotein Complexes / metabolism
  • Mutation

Substances

  • Core Binding Factor Alpha 1 Subunit
  • Fungal Proteins
  • Multiprotein Complexes
  • Iron
  • Cyclin-Dependent Kinases

Grants and funding

This study was funded by an Astellas Infectious Diseases Society of America ERF/NFID Young Investigator Award (http://www.idsociety.org/Index.aspx), a Hellman Family Foundation Early-Career Faculty Award, and a Burroughs Wellcome Career Award in the Biomedical Sciences (http://www.bwfund.org/). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.