The CCAAT-binding complex coordinates the oxidative stress response in eukaryotes

Abstract

The heterotrimeric CCAAT-binding complex is evolutionary conserved in eukaryotic organisms. The corresponding Aspergillus nidulans CCAAT- binding factor (AnCF) consists of the subunits HapB, HapC and HapE. All of the three subunits are necessary for DNA binding. Here, we demonstrate that AnCF senses the redox status of the cell via oxidative modification of thiol groups within the histone fold motif of HapC. Mutational and in vitro interaction analyses revealed that two of these cysteine residues are indispensable for stable HapC/HapE subcomplex formation and high-affinity DNA binding of AnCF. Oxidized HapC is unable to participate in AnCF assembly and localizes in the cytoplasm, but can be recycled by the thioredoxin system in vitro and in vivo. Furthermore, deletion of the hapC gene led to an impaired oxidative stress response. Therefore, the central transcription factor AnCF is regulated at the post-transcriptional level by the redox status of the cell serving for a coordinated activation and deactivation of antioxidative defense mechanisms including the specific transcriptional activator NapA, production of enzymes such as catalase, thioredoxin or peroxiredoxin, and maintenance of a distinct glutathione homeostasis. The underlying fine-tuned mechanism very likely represents a general feature of the CCAAT-binding complexes in eukaryotes.

Deciphering the Combinatorial DNA-binding Code of the CCAAT-binding Complex and the Iron-regulatory Basic Region Leucine Zipper (bZIP) Transcription Factor HapX

“…Conversely, the N-terminal domain of the CBC subunit HapE that is required for interaction with the N terminus of HapX is likewise present only in HapX-employing fungal species. The CBC is a global regulatory complex involved in control of a wide range of processes (12,31), whereas the CBC-HapX complex appears to be involved exclusively in iron regulation.…”

“…In A. nidulans, the CBC consists of the subunits HapB, HapC, and HapE (10) that together bind CCAAT boxes in a limited number of gene promoter sequences identified so far (11,12). Genome-wide identification in human cells resulted in 5000 -15,000 NF-Y-binding sites depending on the cell type, but only 25% of these NF-Y sites mapped to promoter regions (13).…”

Diverse Hap43-Independent Functions of the Candida albicans CCAAT-Binding Complex

“…In fungal eukaryotes, most studies on CBC have focused on the cooperation of CBC with Hap43/HapX in regulating iron homeostasis and expression of iron-responsive genes. However, a recent study demonstrated that A. nidulans CBC also serves as a redox sensor that coordinates with cellular oxidative responses (33), suggesting that fungal CBC may possess functions other than iron-responsive and HapX-dependent functions.…”

Comparative Transcriptome Analysis of Two Olive Cultivars in Response to Nacl Stress

“…The third regulator, transcript se023_D5, showed 95% similarity to a CCAAT-binding transcription factor. CCAAT elements are bound by nuclear factor Y (NF-Y) including a DR1 protein [48] which plays an important role in the endoplasmic reticulumresponse in Arabidopsis [49] and oxidative stress response in eukaryotes [50].…”