Mth1

Mth1 is a transcriptional regulator in the budding yeast Saccharomyces cerevisiae. It functions as a corepressor of the Rgt1 transcription factor to control the expression of hexose transporter genes (HXT). Through its interaction with Rgt1 at HXT promoters, Mth1 helps keep HXT gene expression repressed when glucose is scarce, thereby modulating glucose uptake and cellular metabolism.

In response to abundant glucose, a glucose-sensing pathway involving Snf3 and Rgt2 initiates a signaling cascade that leads to the phosphorylation and SCF(Grr1)-dependent ubiquitination and degradation of Mth1 (and its paralog Std1). This degradation relieves Rgt1-mediated repression and allows activation of HXT gene expression, increasing the cell’s capacity to import glucose. The regulatory system thus couples environmental glucose availability to changes in transporter gene expression.

Genetically, Mth1 and Std1 act redundantly as corepressors of HXT genes. Deletion of MTH1 alone produces modest derepression, while concurrent loss of both Mth1 and Std1 leads to stronger, constitutive expression of HXT genes, even in low-glucose conditions. This pathway is a central component of the yeast glucose signaling network and helps coordinate nutrient uptake with metabolic needs.

Mth1 is conserved within Saccharomycotina fungi, though the specifics of regulation and target genes can vary among species. In research contexts, Mth1 is often discussed alongside Rgt1, Std1, Snf3, Rgt2, and the SCF(Grr1) ubiquitin ligase as part of the glucose-sensing and transporter-regulation module.