The hypoxic expression of the glucose transporter RAG1 reveals the role of the bHLH transcription factor Sck1 as a novel hypoxic modulator in Kluyveromyces lactis

Abstract

Glucose is the preferred nutrient for most living cells and is also a signaling molecule that modulates several cellular processes. Glucose regulates the expression of glucose permease genes in yeasts through signaling pathways dependent on plasma membrane glucose sensors. In the yeast Kluyveromyces lactis, sufficient levels of glucose induction of the low-affinity glucose transporter RAG1 gene also depends on a functional glycolysis, suggesting additional intracellular signaling. We have found that the expression of RAG1 gene is also induced by hypoxia in the presence of glucose, indicating that glucose and oxygen signaling pathways are interconnected. In this study we investigated the molecular mechanisms underlying this crosstalk. By analyzing RAG1 expression in various K. lactis mutants, we found that the bHLH transcriptional activator Sck1 is required for the hypoxic induction of RAG1 gene. The RAG1 promoter region essential for its hypoxic induction was identified by promoter deletion experiments. Taken together, these results show that the RAG1 glucose permease gene is synergistically induced by hypoxia and glucose and highlighted a novel role for the transcriptional activator Sck1 as a key mediator in this mechanism.

Light-Stress Response Mediated by the Transcription Factor KlMga2 in the Yeast Kluyveromyces lactis

“…The experiments were then conducted using the Rotor Gene Q (Qiagen), and data were analyzed using the provided software. The cycling was set with 3 min at 95 • C for enzyme activation, then 40 cycles at 95 • C for 3 s and 30 s at 60 • C, followed by a final step for generation of melting curve, ranging from 60 • to 95 • C. Quantification was performed by the construction of a standard curve with genomic DNA from MWL9S1 with five points of serial dilutions (the R2 obtained for the curve was always higher than 0.99) and by the relative quantification of the samples of interest, using amplification of 18S rDNA as reference (Santomartino et al, 2019b).…”

Genetic and Physiological Characterization of Fructose-1,6-Bisphosphate Aldolase and Glyceraldehyde-3-Phosphate Dehydrogenase in the Crabtree-Negative Yeast Kluyveromyces lactis

“…Both deletions impaired the regulation of the RAG1 gene, identifying the glycolytic flux as an important factor [ 24 ]. RAG1 gene expression is also subject to regulation by oxygen availability, mediated by the transcription factor Sck1 [ 25 ]. In contrast, KlHxk1 appears to be more directly involved in mediating glucose repression [ 26 , 27 ].…”