Regulation of Alternative Carbon Metabolism In Candida Albicans

<p><em>Candida albicans</em> is the most important fungal pathogen of humans. Transcript profiling studies show that upon phagocytosis by macrophages, <em>C. albicans</em> undergoes a massive metabolic reorganization activating genes involved in alternative carbon metabolism, including the glyoxylate cycle, β-oxidation and gluconeogenesis. Mutations in key enzymes such as ICL1 (glyoxylate cycle) and FOX2 (fatty acid β-oxidation) revealed that alternative carbon metabolic pathways are required for full virulence in<em> C. albicans</em>. These studies indicate <em>C. albicans</em> uses non-preferred carbon sources allowing its adaptation to microenvironments were nutrients are scarce. It has become apparent that the regulatory networks required for regulation of alternative carbon metabolism in <em>C. albicans</em> are considerably different from the <em>Saccharomyces cerevisiae</em> paradigm and appear more analogous to the <em>Aspergillus nidulans</em> systems. Well-characterized transcription factors in <em>S. cerevisiae</em> have no apparent phenotype or are missing in<em> C. albicans</em>.</p> <p>CTF1 was found to be a single functional homolog of the <em>A. nidulans</em> FarA/FarB proteins, which are transcription factors required for fatty acid utilization. Both <em>FOX2</em> and <em>ICL1</em> were found to be part of a large CTF1 regulon. To increase our understanding of how CTF1 regulates its target genes, including whether regulation is direct or indirect, the <em>FOX2</em> and <em>ICL1</em> promoter regions were analyzed using a combination of bioinformatics and promoter deletion analysis. To begin characterizing the <em>FOX2</em> and <em>ICL1</em> promoters, 5’ rapid amplification of cDNA ends (5’RACE) was used to identify two transcriptional initiation sites in <em>FOX2</em> and one in <em>ICL1</em>. GFP reporter assays show <em>FOX2</em> and <em>ICL1</em> are rapidly expressed in the presence of alternative carbon sources. Both <em>FOX2</em> and <em>ICL1</em> harbor the CCTCGG sequence known to be bound by the Far proteins, hence rendering the motif as a putative CTF1 DNA binding element. In this study, the CCTCGG sequence was found to be essential for <em>FOX2</em> regulation. However, this motif does not appear to be equally important for the regulation of <em>ICL1</em>. This study supports the notion that although <em>C. albicans</em> has diverged from the<em> </em>paradigms of model fungi, <em>C. albicans</em> has made specific adaptations to its transcription-based regulatory network that may contribute to its metabolic flexibility.</p>

Name thesis:degree_name

Masters of Science (MS)

Level thesis:degree_level

Thesis (MS)

Year dc:date.available

2012

Author dc:creator

• Gonzalez, Arely Y

Contributors dc:contributor

• Michael C. Lorenz, Ph.D.
• Kevin Morano, Ph.D.
• Hung Ton-That, Ph.D.

• regulation of carbon metabolism in fungi
• promoter dissection
• Genetics and Genomics
• Microbiology

Repository record dc:identifier

https://digitalcommons.library.tmc.edu/utgsbs_dissertations/316

OAI identifier oai:identifier

oai:digitalcommons.library.tmc.edu:utgsbs_dissertations-1351