Casein Kinase I Isoform Hrr25 Is a Negative Regulator of Haa1 in the Weak Acid Stress Response Pathway in Saccharomyces cerevisiae

Abstract

Haa1 is a transcription factor that adapts cells to weak organic acid stresses by activating the expression of various genes. Many of these genes encode membrane proteins, such as and How Haa1 is activated by weak acids is not clear. Here, we show that casein kinase I isoform Hrr25 is an important negative regulator of Haa1. Haa1 is known to be multiply phosphorylated. We found that mutations in lead to reduced Haa1 phosphorylation and increased expression of Haa1 target genes and that Hrr25 interacts with Haa1. The other three casein kinase I isoforms, Yck1, Yck2, and Yck3, do not seem to play critical roles in Haa1 regulation. Hrr25 has a 200-residue C-terminal region, including a proline- and glutamine-rich domain. Our data suggest that the C-terminal region of Hrr25 is required for normal inhibition of expression of Haa1 target genes and and is important for cell growth but is not required for cell morphogenesis. We propose that Hrr25 is an important regulator of cellular adaptation to weak acid stress by inhibiting Haa1 through phosphorylation. Our study has revealed the casein kinase I protein Hrr25 to be a negative regulator of Haa1, a transcription factor mediating the cellular response to stresses caused by weak acids. Many studies have focused on the target genes of Haa1 and their roles in weak acid stress responses, but little has been reported on the regulatory mechanism of Haa1. Weak acids, such as acetic acid, have long been used for food preservation by slowing down the growth of fungal species, including In the biofuel industry, acetic acid in the lignocellulosic hydrolysates limits the production of ethanol, which is undesirable. By understanding how Haa1 is regulated, we can make advances in the field of food sciences to better preserve food and engineer acetic acid-resistant strains that will increase productivity in the biofuel industry.

Adaptive Response and Tolerance to Acetic Acid in Saccharomyces cerevisiae and Zygosaccharomyces bailii: A Physiological Genomics Perspective

“…The rapid translocation of Haa1 from the cytosol to the nucleus, where it activates the transcription of its target-genes in response to lactic ( Sugiyama et al, 2014 ) or acetic ( Swinnen et al, 2017 ) acids, is concomitant with a decrease in Haa1 phosphorylation levels ( Sugiyama et al, 2014 ). The casein kinase I isoform Hrr25 is an important negative regulator of Haa1, inhibiting this transcription factor’s activity by phosphorylation ( Collins et al, 2017 ). It was also demonstrated that the exportin Msn5, which preferentially exports phosphorylated cargo proteins, interacts with Haa1 being essential to its exit from the nucleus where its function as transcription factor takes place ( Sugiyama et al, 2014 ) ( Figure 5 ).…”

Activation of Haa1 and War1 transcription factors by differential binding of weak acid anions inSaccharomyces cerevisiae

“…Haa1 translocates from the cytoplasm to the nucleus during acetic acid or lactic acid treatment (20,33). However, it is unknown whether the nuclear localization of Haa1 is the major regulatory step for its activation.…”

“…Ace1 exists in the nucleus independently of the Cu status, and Cu(I) binding converts an inactive Ace1 to a functional protein capable of DNA binding and activating transcription (30,76,77). In contrast, Haa1 translocates from the cytoplasm to the nucleus by an as yet unidentified mechanism during weak acid stress (20,33). Haa1, which was localized in the nucleus in the msn5 Δ mutant, exhibited reduced stability (Figure 2B).…”

“…Instead of Cu-dependent regulation, Haa1 is involved in cellular protection from hydrophilic weak acids such as acetic acid and lactic acid by inducing the transcription of genes such as TPO2 and TPO3 , which encode the major facilitator superfamily of transporters involved in the export of acid anions (2,20,22,23). Haa1 rapidly relocates from the cytoplasm to the nucleus during acetic acid- or lactic acid-induced stress, concurrent with some changes to the phosphorylation status (20,33). However, it is not known how Haa1 is activated in response to weak acids.…”

Effect of Dissolved Oxygen and Acid on the Yield of 2,3-butanediol by Saccharomyces Cerevisiae W141

“…However, S. cerevisiae commonly encounters acid stress in industrial settings, which will greatly affect the redox balance in the cell and metabolite yields [16][17][18]. The acid stress response mechanism of yeast cells includes the following four aspects: (1) the cell membrane maintains the stability of intracellular pH by restricting the penetration of high levels of acid; (2) the cell membrane channel proteins that regulates transcription factors and acid transport maintains the intracellular stabilization of pH; (3) adenosine triphosphatase H + -ATPase (encoded by the PMA1 gene) on the cell membrane can hydrolyse ATP to produce energy, pumping protons out of the cell to maintain a normal neutral pH environment in the cell; and (4) maintaining the integrity and uidity of cell membranes by modulating fatty acid composition [13,19,20]. Among these processes, maintaining the stability of intracellular pH through the massive consumption of ATP in the cell is the most important, but the results obtained using this method will lead to intracellular acidi cation, thereby inhibiting cell growth and metabolism, especially for the TCA cycle, with the Crabtree effect having the most notable in uence [12,19,21].…”