Differential regulation of two myo‐inositol transporter genes of Saccharomyces cerevisiae

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Abstract
We previously isolated two distinct Saccharomyces cerevisiae myo-inositol transporter genes, ITR1 and ITR2 (Nikawa et al., 1991). Here, we studied the regulation of their expression by measuring steady-state mRNA levels and β-galactosidase activities of lacZ fusion genes under different conditions. The results show that the expression of the two ITR genes is differently regulated: ITR1 was repressed by inositol and choline whereas ITR2 was constitutive. Deletion analysis of the ITR1 upstream region and comparison with the upstream regions of other genes involved in phospholipid synthesis indicate that the octamer sequence 5′-TTCACATG-3′ is important for the expression and inositol/choline regulation of the ITR1 gene.