Perturbation of the interaction between Gal4p and Gal80p of the Saccharomyces cerevisiae GAL switch results in altered responses to galactose and glucose

• Published in: Molecular microbiology 2014-10, Vol.94 (1), p.202-217
• Main Authors: Das Adhikari, Akshay Kumar, Qureshi, Mohd. Tanvir, Kar, Rajesh Kumar, Bhat, Paike Jayadeva
• Format: Article
• Language: English
• Subjects: DNA-Binding Proteins - genetics; DNA-Binding Proteins - metabolism; Galactose - metabolism; Gene expression; Gene Expression Regulation, Fungal; Genomics; Glucose; Glucose - metabolism; Kinases; Protein Binding; Repressor Proteins - genetics; Repressor Proteins - metabolism; Saccharomyces cerevisiae - genetics; Saccharomyces cerevisiae - metabolism; Saccharomyces cerevisiae Proteins - genetics; Saccharomyces cerevisiae Proteins - metabolism; Signal transduction; Transcription Factors - genetics; Transcription Factors - metabolism; Yeast
• ISSN: 0950-382X; 1365-2958
• DOI: 10.1111/mmi.12757

Summary In S. cerevisiae, following the Whole Genome Duplication (WGD), GAL1‐encoded galactokinase retained its signal transduction function but lost basal expression. On the other hand, its paralogue GAL3, lost kinase activity but retained its signalling function and basal expression, thus making it indispensable for the rapid induction of the S. cerevisiae GAL switch. However, a gal3Δ strain exhibits delayed growth kinetics due to the redundant signalling function of GAL1. The subfunctionalization between the paralogues GAL1 and GAL3 is due to expression divergence and is proposed to be due to the alteration in the Upstream Activating Sequences (UASG). We demonstrate that the GAL switch becomes independent of GAL3 by altering the interaction between Gal4p and Gal80p without altering the configuration of UASG. In addition to the above, the altered switch of S. cerevisiae loses ultrasensitivity and stringent glucose repression. These changes caused an increase in fitness in the disaccharide melibiose at the expense of a decrease in fitness in galactose. The above altered features of the ScGAL switch are similar to the features of the GAL switch of K. lactis that diverged from S. cerevisiae before the WGD.