Yap7 is a transcriptional repressor of nitric oxide oxidase in yeasts, which arose from neofunctionalization after whole genome duplication

Abstract

SummaryFlavohemoglobins are the main detoxifiers of nitric oxide (NO) in bacteria and fungi and are induced in response to nitrosative stress. In fungi, the flavohemoglobin encoding gene YHB1 is positively regulated by transcription factors which are activated upon NO exposure. In this study, we show that in the model yeast Saccharomyces cerevisiae and in the human pathogen Candida glabrata, the transcription factor Yap7 constitutively represses YHB1 by binding its promoter. Consequently, YAP7 deletion conferred high NO resistance to the cells. Coimmunoprecipitation experiments and mutant analyses indicated that Yap7 represses YHB1 by recruiting the transcriptional repressor Tup1. In S. cerevisiae, YHB1 repression also involves interaction of Yap7 with the Hap2/3/5 complex through a conserved Hap4-like-bZIP domain, but this interaction has been lost in C. glabrata. The evolutionary origin of this regulation was investigated by functional analyses of Yap7 and of its paralogue Yap5 in different yeast species. These analyses indicated that the negative regulation of YHB1 by Yap7 arose by neofunctionalization after the whole genome duplication which led to the C. glabrata and S. cerevisiae extant species. This work describes a new aspect of the regulation of fungal nitric oxidase and provides detailed insights into its functioning and evolution.

The CCAAT-Binding Complex Controls Respiratory Gene Expression and Iron Homeostasis in Candida Glabrata

“…We observed that the absence of Hap5 totally abolished Yap5 binding to its target. In a previous work, we noticed that Yap5 contains a degenerated but still recognizable Hap4L motif just upstream of its bZIP domain 21 . This motif corresponds to the N-terminal half of the canonical Hap4L domain (Fig.…”

“…In S. cerevisiae and C. glabrata , iron stress response has been shown to be controlled by the Yap5 bZIP transcription factor 21, 34–36 . This regulation absolutely requires the direct binding of Yap5 to YRE motifs (TTACTAA) in the promoters of these genes 29, 34, 35 .…”

“…HapX acts by repressing the expression of iron consuming genes in iron starvation conditions and by activating these genes in iron excess 11, 13, 17, 18, 20 . HapX proteins have few similarity with Hap4 except for the 16 amino acids domain (called Hap4Like or Hap4L) which is required for their interaction with Hap5 12, 18, 21, 22 . In addition, they also have a bZIP DNA binding domain similar to the one found in the oxidative stress response factor Yap1 12, 18, 21–23 .…”

“…HapX proteins have few similarity with Hap4 except for the 16 amino acids domain (called Hap4Like or Hap4L) which is required for their interaction with Hap5 12, 18, 21, 22 . In addition, they also have a bZIP DNA binding domain similar to the one found in the oxidative stress response factor Yap1 12, 18, 21–23 . In Yap1, this domain is responsible for the specific recognition of the YRE (Yap Response Element) DNA motif (TTACTAA).…”

“…A potential ortholog of Hap43/HapX, named Yap7, has been identified in S. cerevisiae 18, 23 , but it is not directly involved in iron starvation or iron excess responses 21 .…”