The regulation of Snf3 in S. cerevisiae and its downstream events are still poorly understood, but it seems clear that a second glucose sensor Rgt2 influences Snf3 and vice versa.  Furthermore, it is unclear whether these two proteins sense the glucose concentration on the outside or inside the cell.  Snf3 and Rgt2 influence directly or indirectly several Hxt-transporters which are responsible for the glucose uptake.  Low extracellular glucose concentrations are sensed by the Snf3 protein which probably leads to the expression of Hxt2-Genes for high affinity glucose transporters, while Rgt2 senses high glucose concentrations and leads to the expression of low affinity glucose transporters, like Hxt1  Although the downstream pathway is poorly understood it seems that Snf3 and Rgt2 transmit a signal directly or indirectly to Grr1, the DNA binding protein Rgt1, and the two cofactors Ssn6 and Tup1.  Also needed for the transcription are the two nuclear proteins Mth1 and Std1.