Chakravarti Ananya, Camp Kyle, McNabb David S, Pinto Inés
Department of Biological Sciences, University of Arkansas, Fayetteville, Arkansas, United States of America.
Cell and Molecular Biology Program, University of Arkansas, Fayetteville, Arkansas, United States of America.
PLoS One. 2017 Jan 25;12(1):e0170649. doi: 10.1371/journal.pone.0170649. eCollection 2017.
Candida albicans is the most frequently encountered fungal pathogen in humans, capable of causing mucocutaneous and systemic infections in immunocompromised individuals. C. albicans virulence is influenced by multiple factors. Importantly, iron acquisition and avoidance of the immune oxidative burst are two critical barriers for survival in the host. Prior studies using whole genome microarray expression data indicated that the CCAAT-binding factor is involved in the regulation of iron uptake/utilization and the oxidative stress response. This study examines directly the role of the CCAAT-binding factor in regulating the expression of oxidative stress genes in response to iron availability. The CCAAT-binding factor is a heterooligomeric transcription factor previously shown to regulate genes involved in respiration and iron uptake/utilization in C. albicans. Since these pathways directly influence the level of free radicals, it seemed plausible the CCAAT-binding factor regulates genes necessary for the oxidative stress response. In this study, we show the CCAAT-binding factor is involved in regulating some oxidative stress genes in response to iron availability, including CAT1, SOD4, GRX5, and TRX1. We also show that CAT1 expression and catalase activity correlate with the survival of C. albicans to oxidative stress, providing a connection between iron obtainability and the oxidative stress response. We further explore the role of the various CCAAT-binding factor subunits in the formation of distinct protein complexes that modulate the transcription of CAT1 in response to iron. We find that Hap31 and Hap32 can compensate for each other in the formation of an active transcriptional complex; however, they play distinct roles in the oxidative stress response during iron limitation. Moreover, Hap43 was found to be solely responsible for the repression observed under iron deprivation.
白色念珠菌是人类最常遇到的真菌病原体，能够在免疫功能低下的个体中引起黏膜皮肤感染和全身感染。白色念珠菌的毒力受多种因素影响。重要的是，获取铁和避免免疫氧化爆发是在宿主体内存活的两个关键障碍。先前使用全基因组微阵列表达数据的研究表明，CCAAT结合因子参与铁摄取/利用的调节以及氧化应激反应。本研究直接考察CCAAT结合因子在响应铁可用性时调节氧化应激基因表达中的作用。CCAAT结合因子是一种异源寡聚转录因子，先前已证明其可调节白色念珠菌中参与呼吸作用以及铁摄取/利用的基因。由于这些途径直接影响自由基水平，因此CCAAT结合因子调节氧化应激反应所需基因似乎是合理的。在本研究中，我们表明CCAAT结合因子参与响应铁可用性调节一些氧化应激基因，包括CAT1、SOD4、GRX5和TRX1。我们还表明，CAT1表达和过氧化氢酶活性与白色念珠菌对氧化应激的存活能力相关，这在铁的可获得性和氧化应激反应之间建立了联系。我们进一步探讨了各种CCAAT结合因子亚基在形成不同蛋白质复合物中的作用，这些复合物可响应铁调节CAT1的转录。我们发现Hap31和Hap32在形成活性转录复合物时可以相互补偿；然而，它们在铁限制期间的氧化应激反应中发挥不同作用。此外，发现Hap43是铁缺乏时观察到的抑制作用的唯一原因。
