S. Ozcan et M. Johnston, 2 DIFFERENT REPRESSORS COLLABORATE TO RESTRICT EXPRESSION OF THE YEAST GLUCOSE-TRANSPORTER GENES HXT2 AND HXT4 TO LOW-LEVELS OF GLUCOSE, Molecular and cellular biology, 16(10), 1996, pp. 5536-5545
Transcription of the yeast HXT2 and HXT4 genes, which encode glucose t
ransporters, is induced only by low levels of glucose, This low-glucos
e-induced expression is mediated by tyro independent repression mechan
isms: in the absence of glucose, transcription of both genes is preven
ted by Rgt1p, a C-6 zinc cluster protein; at high levels of glucose, e
xpression of HXT2 and HXT4 is repressed by Mig1p. Only at low glucose
concentrations are both repressors inactive, leading to a 10- to 20-fo
ld induction of gene expression, Mig1p and Rgt1p act directly on HXT2
and HXT4 by binding to their promoters, This transcriptional regulatio
n is physiologically very important to the yeast cell because it cause
s these glucose transporters to he expressed only in low-glucose media
, in which they are required for growth.