Pl. Blaiseau et al., Aft2p, a novel iron-regulated transcription activator that modulates, withAft1p, intracellular iron use and resistance to oxidative stress in yeast., J BIOL CHEM, 276(36), 2001, pp. 34221-34226
The yeast, Saccharomyces cerevisiae, contains a transcription activator, Af
t1p, that regulates the transcription of the high affinity iron transport s
ystem genes. This report describes the properties of Aft2p, a protein 39% h
omologous to Aft1p. Aft2p was found to activate transcription. Overproducti
on of Aft2p activates the transcription of the AFT1 target gene FET3. The d
ouble aft1aft2 mutant was unable to grow in iron-deprived conditions. Becau
se a fet3 mutant does not show this deficiency, the defect is not solely ca
used by mis-regulation of iron transport but also involves defective iron u
se by the cells. The aft1 cells were unable to grow in aerobic conditions o
n plates containing raffinose as the sole carbon source. The inability to g
row on raffinose is not caused by the cell iron content being too low to su
stain respiratory metabolism, because the oxygen consumption of aft1 mutant
s showed that their respiratory activity is 2-fold higher than that of cont
rols. The double aft1aft2 mutant also has many phenotypes related to oxidat
ive stress such as H2O2 hypersensitivity, oxygen-dependent copper toxicity,
and oxygen-dependent methionine auxotrophy, which are suppressed in anaero
biosis. These results suggest that Aft2p and Aft1p have overlapping roles i
n the control of iron-regulated pathway(s) connected to oxidative stress re
sistance in yeast.