Mth1 receives the Signal given by the glucose sensors Snf3 and Rgt2 in Saccharomyces cerevisiae

We have determined that the mutant genes DGT1-1 and BPC1-1, which impair gl ucose transport and catabolite repression in Saccharomyces cerevisiae, are allelic forms of MTH1. Deletion of MTH1 had only slight effects on the expr ession of HXT1 or SNF3, but increased expression of HXT2 in the absence of glucose. A two-hybrid screen revealed that the Mth1 protein interacts with the cytoplasmic tails of the glucose sensors Snf3 and Rgt2. This interactio n was affected by mutations in Mth1 and by the concentration of glucose in the medium. A double mutant, snf3 rgt2, recovered sensitivity to glucose wh en MTH1 was deleted, thus showing that glucose signalling may occur indepen dently of Snf3 and Rgt2. A model for the possible mode of action of Snf3 an d Rgt2 is presented.