Glucose sensing through the Hxk2-dependent signalling pathway.

In this work, we describe the hexokinase 2 (Hxk2) signalling pathway within the yeast cell. Hxk2 and Mig1 are the two major factors of glucose repression in Saccharomyces cerevisiae. The functions of both proteins have been extensively studied but there is no information about possible interactions among them in the repression pathway. Our results demonstrate that Hxk2 interacts directly with Mig1 in vivo and in vitro and that the ten amino acids motif between K6 and M15 is required for their interaction. This interaction has been detected at the DNA level both in vivo by chromatin immunoprecipitation experiments and in vitro using purified proteins and a DNA fragment containing the MIG1 site of the SUC2 promoter. This demonstrates that the interaction is of physiological relevance. Our findings show that the main role of Hxk2 in the glucose signalling pathway is the interaction with Mig1 to generate a repressor complex located in the nucleus of S. cerevisiae.