High impact information on OPI1

• These data suggest that the OPI1 gene product is the primary target (sensor) of the inositol response and that derepression of INO2 transcription determines the degree of expression of the target genes [1].
• Furthermore, the effect of inositol on target gene expression was eliminated by deleting the OPI1 gene in the GAL1-INO2-containing strain [1].
• Our data show that derepression of phospholipid biosynthetic gene expression involves two mechanisms: increasing the levels of the INO2 and INO4 gene products and inactivating the OPI1-mediated repression mechanism [2].
• In the presence of inositol and choline (repressing), the product of the OPI1 gene represses transcription dictated by the UASINO element [2].
• Another regulatory mutation, opi1, which causes the constitutive derepression of PSS and other phospholipid biosynthetic enzymes, caused the constitutive derepression of the 1.2-kb RNA [3].

Biological context of OPI1

• The promoter region of OPI1 contains one copy of ICRE, and here we analyzed the involvement of ICRE in the inositol-choline-mediated gene regulation of OPI1 [4].
• INO2 expression is regulated by a complex cascade that includes autoregulation, Opi1p-mediated repression and Ume6p-mediated activation [5].
• Overproduction of the Opi1 repressor inhibits transcriptional activation of structural genes required for phospholipid biosynthesis in the yeast Saccharomyces cerevisiae [6].
• Furthermore, the OPI1 gene was found to be nonessential to the organism since mutants bearing the null allele were viable and exhibited a phenotype similar to that of previously isolated opi1 mutants [7].
• The cloned OPI1 gene was sequenced, and translation of the open reading frame predicted a protein composed of 404 amino acid residues with a molecular weight of 40,036 [7].

Anatomical context of OPI1

• Opi1p is a repressor of the phospholipid biosynthetic genes and specifically binds PA in the endoplasmic reticulum [8].

Associations of OPI1 with chemical compounds

• Although the leucine zipper suggests that Opi1 may act as a DNA-binding protein, our data do not support a direct interaction with the ICRE [6].
• Opi1 contains a leucine zipper motif and two glutamine-rich stretches [6].
• In Saccharomyces cerevisiae, recessive mutations at the OPI1 locus result in constitutively derepressed expression of inositol 1-phosphate synthase, the product of the INO1 gene [7].
• The OPI1 gene of Saccharomyces cerevisiae, a negative regulator of phospholipid biosynthesis, encodes a protein containing polyglutamine tracts and a leucine zipper [7].
• The negative regulator Opi1p mediates repression of the GUT1 promoter, whereas the effects of the glucose repressors Mig1p and Mig2p are minor [9].

Physical interactions of OPI1

• Results of an in vitro assay have led to a model in which Opi1p interacts with Ino2p [10].

Regulatory relationships of OPI1

• Mutation of the specific negative regulator of phospholipid synthesis encoded by OPI1 suppressed the inositol auxotrophy of swi2 mutants [11].
• Overexpression of OPI1 under control of the GAL1 promoter severely inhibited activation of ICRE-dependent genes, leading to inositol-requiring cells [6].
• Here we have studied the FFAT-VAP interaction in Saccharomyces cerevisiae, where the VAP homologue Scs2 regulates phospholipid metabolism via an interaction with the FFAT motif of Opi1 [12].
• Consequently, the corresponding dominant Ino2 variants conferred constitutive expression of an ICRE-dependent reporter gene and were no longer inhibited even by overproduction of Opi1 [13].
• Phosphatidylinositol synthase was not found to be regulated in either wild-type or opi1 cells [14].

Other interactions of OPI1

• We tested the hypothesis that N-myristoylproteins function to regulate INO2, INO4 and/or OPI1 transcription, thereby affecting the expression of inositol-sensitive genes that influence myristoylCoA metabolism [15].
• We also show that the UME6 gene does not affect the expression of an OPI1-cat reporter [5].
• OPI1 encodes a repressor of INO1 transcription [16].
• The decrease was due to repression of ITR1 transcription, independent of the negative regulator Opi1p, and degradation of the existing permease [17].
• Using in vivo as well as in vitro interaction assays, we show binding of the pleiotropic repressor Sin3 to the pathway-specific regulator Opi1 [18].

References