Identification of the Candida albicans Cap1p Regulon

Abstract

Cap1p, a transcription factor of the basic region leucine zipper family, regulates the oxidative stress response (OSR) in Candida albicans. Alteration of its C-terminal cysteine-rich domain (CRD) results in Cap1p nuclear retention and transcriptional activation. To better understand the function of Cap1p in C. albicans, we used genome-wide location profiling (chromatin immunoprecipitation-on-chip) to identify its transcriptional targets in vivo. A triple-hemagglutinin (HA 3 ) epitope was introduced at the C terminus of wild-type Cap1p (Cap1p-HA 3 ) or hyperactive Cap1p with an altered CRD (Cap1p-CSE-HA 3 ). Location profiling using wholegenome oligonucleotide tiling microarrays identified 89 targets bound by Cap1p-HA 3 or Cap1p-CSE-HA 3 (the binding ratio was at least twofold; P < 0.01). Strikingly, Cap1p binding was detected not only at the promoter region of its target genes but also at their 3 ends and within their open reading frames, suggesting that Cap1p may associate with the transcriptional or chromatin remodeling machinery to exert its activity. Overrepresented functional groups of the Cap1p targets (P < 0.02) included 11 genes involved in the OSR (CAP1, GLR1, TRX1, SOD1, CAT1, and others), 13 genes involved in response to drugs (PDR16, MDR1, FLU1, YCF1, FCR1, and others), 4 genes involved in phospholipid transport (PDR16, GIT1, RTA2, and orf19.932), and 3 genes involved in the regulation of nitrogen utilization (GST3, orf19.2693, and orf19.3121), suggesting that Cap1p has other cellular functions in addition to the OSR. Bioinformatic analyses of the bound sequences suggest that Cap1p recognizes the DNA motif 5-MTKASTMA. Finally, transcriptome analyses showed that increased expression generally accompanies Cap1p binding at its targets, indicating that Cap1p functions as a transcriptional activator.Candida albicans is an opportunistic human fungal pathogen that causes superficial infections in healthy patients. However, in patients with impaired immunity C. albicans can cause lifethreatening invasive infections, including systemic candidiasis or candidemia. In the United States, candidemia represents the fourth-most-common cause of nosocomial bloodstream infections (7). Several options for the treatment of invasive candidiasis are available to clinicians, including the administration of azole derivatives, amphotericin B preparations, or echinocandin antifungal agents, while for the treatment of mucocutaneous infections, azoles are preferred over other antifungals due to their low toxicity and increased efficacy and availability for both topical and oral use (21, 50).Azoles, including both imidazoles (e.g., ketoconazole) and triazoles (e.g., fluconazole [FLC]), inhibit the function of the lanosterol demethylase enzyme Erg11p, a component of the ergosterol biosynthesis pathway, leading to methylsterol accumulation, sterol depletion, and consequently to growth arrest (1). This fungistatic property of azoles coupled to their repeated use in the clinic renders the surviving C. albicans cells prone to the sele...

A comprehensive functional portrait of two heat shock factor-type transcriptional regulators involved in Candida albicans morphogenesis and virulence

“…Western blot analyses of strains grown under P MET3 -inducing conditions showed that both Sfl1p-HA 3 and Sfl2p-HA 3 fusion proteins were expressed ( Figure 1B, lanes 4 and 6). As an additional control for signal specificity, immunoblotting of total extracts from a C. albicans strain expressing the Cap1p-HA 3 fusion ( Figure 1, lane 2) or the corresponding empty-vector negative control ( Figure 1, lane 1) was used [43].…”

“…(B) Western blot analysis of homozygous sfl1 or sfl2 mutants (sfl1D/sfl1D or sfl2D/sfl2D) expressing HA 3 -tagged versions of the SFL1 or SFL2 genes, respectively (SFL1-HA 3 or SFL2-HA 3 ) together with the corresponding empty vector controls (Vector). The SGY243 strain expressing the CAP1-HA 3 (CAP1-HA 3 ) or carrying the empty vector (Vector) were used as a positive control [43]. Strains were grown overnight in SD medium (P MET3 -inducing conditions) and total protein extracts were prepared then subjected to SDS-PAGE.…”

Role of the Yap Family in the Transcriptional Response to Oxidative Stress in Yeasts

“…They are respectively named Cgap1p and Cap1p and are also involved in the response to oxidative stress (Chen et al, 2007;Lelandais et al, 2008;Znaidi et al, 2009). Infections caused by fungal pathogens have become major life-threatening diseases, especially in patients with defects in their immune system.…”

“…These sets of genes are referred to as AP-1 transcriptional modules (TMs). In each yeast species, benomyl is known to activate an oxidative stress, for which the genomic response of the cell is primarily dependant on the TFs Yap1p (Lucau-Danila et al, 2005), Cgap1p and Cap1p (Znaidi et al, 2009). To summarize, our strategy consisted in considering three different layers of information based on the analysis of genome-wide datasets.…”

“…Azole antifungals, especially fluconazole, were widely used to treat these fungal diseases, but rapidly an important number of clinical drug resistance cases was reported (White et al, 1998). Recently, it was proposed that drug resistance and the response to oxidative stress are interconnected processes in C. albicans (Znaidi et al, 2009). This connection exists through the activity of several TFs like Cap1p, Tac1p, Mrr1p or Upc2p for which (i) gain-of-function mutations were observed as being related to clinical azole resistance and (ii) genome-wide studies identified several of their target genes as being involved in the general response to oxidative stress Morschhauser et al, 2007;Znaidi et al, 2009;Znaidi et al, 2008).…”