High impact information on ITR1

• The interactions between two myosin proteins, UNC-54 and MYO-1, and ITR-1 were identified in a yeast two-hybrid screen and subsequently confirmed in vivo and in vitro [1].
• The decrease was due to repression of ITR1 transcription, independent of the negative regulator Opi1p, and degradation of the existing permease [2].
• Uptake of inositol by Saccharomyces cerevisiae is mediated by a specific inositol permease encoded by the ITR1 gene [3].
• Thus, inactivation of the Itr1 permease is accompanied by endocytic internalization followed by degradation in the vacuole [3].
• By the complementation of a yeast mutant defective in myo-inositol transport (Nikawa, J., Nagumo, T., and Yamashita, S. (1982) J. Bacteriol. 150, 441-446), we isolated two myo-inositol transporter genes, ITR1 and ITR2, from a yeast gene library [4].

Biological context of ITR1

• A multi-copy plasmid that expresses GFP-fused Itr1p under the control of the original ITR1 promoter was constructed [5].
• The ITR1 and ITR2 genes contained long open reading frames capable of encoding 584 and 612 amino acids with calculated relative molecular masses of 63,605 and 67,041, respectively [4].
• The HvGAMYB protein, expressed in bacteria, binds to oligonucleotides containing the 5'-TAACAAC-3' or 5'-CAACTAAC-3' sequences, derived from the promoter regions of the endosperm-specific genes Hor2 and Itr1, encoding a B-hordein and trypsin-inhibitor BTI-CMe, respectively [6].

Anatomical context of ITR1

• Under inositol-free culture conditions, GFP-fused Itr1p appeared and was localized to the plasma membrane [5].

Associations of ITR1 with chemical compounds

• Removal of inositol from the growth medium results in an increase in ITR1 mRNA abundance [3].
• The expression of many genes of Saccharomyces cerevisiae, such as ITR1, is regulated by inositol and choline [7].
• All mutant genes suppressed the growth defect caused by itr1 disruption, indicating that cysteine residues are not essential for its function [5].
• Eight out of nine cysteine residues in Itr1p, which are common in two transporters, were converted to serine residues by site directed mutagenesis [5].
• Repression of transcription of ITR1 also requires ongoing synthesis of phosphatidylcholine, defining an additional link between synthesis of phospholipids and regulation of inositol uptake [8].

Regulatory relationships of ITR1

• 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 [9].

Other interactions of ITR1

• Gene-disruption experiments revealed that DIE1 was essential for the expression of ITR1 but that DIE2 was not [7].
• Itr1p and Itr2p are high and low affinity transporters, respectively [5].
• In this work, a yeast strain has been constructed in which HIS3 expression is controlled by the ITR1 promoter [7].
• Chimeric genes that express Itr1p and Itr2p fused to the green fluorescent protein (GFP) under the control of the ADH1 promoter were constructed [5].

Analytical, diagnostic and therapeutic context of ITR1

• Northern blot analysis revealed that two of these three genes, designated as DIE1 and DIE2, clearly increased the expression of ITR1 [7].

References