INO1/YJL153C Summary Help

Standard Name INO1 1
Systematic Name YJL153C
Alias APR1
Feature Type ORF, Verified
Description Inositol-3-phosphate synthase; involved in synthesis of inositol phosphates and inositol-containing phospholipids; transcription is coregulated with other phospholipid biosynthetic genes by Ino2p and Ino4p, which bind the UASINO DNA element (2, 3 and see Summary Paragraph)
Name Description INOsitol requiring 1
Chromosomal Location
ChrX:135933 to 134332 | ORF Map | GBrowse
Note: this feature is encoded on the Crick strand.
Genetic position: -101 cM
Gene Ontology Annotations All INO1 GO evidence and references
  View Computational GO annotations for INO1
Molecular Function
Manually curated
Biological Process
Manually curated
Cellular Component
Regulators 7 genes
Classical genetics
reduction of function
Large-scale survey
57 total interaction(s) for 51 unique genes/features.
Physical Interactions
  • Affinity Capture-MS: 4
  • Affinity Capture-RNA: 1
  • PCA: 19
  • Two-hybrid: 2

Genetic Interactions
  • Dosage Rescue: 5
  • Negative Genetic: 15
  • Positive Genetic: 7
  • Synthetic Rescue: 4

Expression Summary
Length (a.a.) 533
Molecular Weight (Da) 59,642
Isoelectric Point (pI) 5.77
Phosphorylation PhosphoGRID | PhosphoPep Database
sequence information
ChrX:135933 to 134332 | ORF Map | GBrowse
Note: this feature is encoded on the Crick strand.
Genetic position: -101 cM
Last Update Coordinates: 2011-02-03 | Sequence: 2003-09-22
Subfeature details
Most Recent Updates
Coordinates Sequence
CDS 1..1602 135933..134332 2011-02-03 2003-09-22
Retrieve sequences
Analyze Sequence
S288C only
S288C vs. other species
S288C vs. other strains
External Links All Associated Seq | E.C. | Entrez Gene | Entrez RefSeq Protein | MIPS | Search all NCBI (Entrez) | UniProtKB
Primary SGDIDS000003689

The INO1 gene encodes inositol-3-phosphate synthase, the enzyme that catalyzes the conversion of glucose 6-phosphate to inositol 3-phosphate (3, 4). During the logarithmic phase of growth, in the absence of inositol from the growth medium, this reaction is rate limiting for the synthesis of inositol-containing phospholipids (5). Inositol phosphates have been shown to play central roles in signal transduction pathways for a variety of neurotransmitters, hormones and growth factors and in mRNA export from nucleus (6).

Expression of the INO1 gene requires binding of Ino2p and Ino4p transcriptional activators to a repeated element, UASINO (Upstream Activating Sequence of INO) (7). This element is found in the promoters of INO1 and other co-regulated genes (such as CHO1, CHO2) of the phospholipid biosynthesis pathway that are subject to regulation by inositol (8). The INO2 and INO4 genes encode basic helix-loop-helix proteins that bind to the UASINO element (consensus sequence- 5'-CATGTGAAAT-3') as a heterodimer (2). When inositol is present, transcription of the INO1 gene is repressed by the negative regulatory protein Opi1p (9). Opi1p does not bind to UASINO directly nor does it interact with Ino2p and Ino4p activators (10). The exact mechanism of repression by Opi1p is unknown, although phosphorylation of Opi1p at Ser26 functions to inactivate Opi1p and mediates attenuation of the negative regulatory function of Opi1p on the expression of the INO1 gene (11). It has been shown that transient nitrogen limitation can also cause INO1 repression (5). INO1 transcription is a sensitive indicator of defects in the cellular transcription apparatus. Mutations in the large subunit of RNA polymerase II, the TATA binding protein (TBP), or components of the SWI/SNF chromatin remodeling complex lead to inositol auxotrophy (Ino- phenotype) due to an inability to activate the INO1 gene (12, 13, 14). It is not yet known which proteins transmit the inositol signal to these transcriptional regulatory factors, due in part to the complexity of overlapping pathways that impinge on INO1 expression.

Last updated: 2003-03-14 Contact SGD

References cited on this page View Complete Literature Guide for INO1
1) Culbertson MR and Henry SA  (1975) Inositol-requiring mutants of Saccharomyces cerevisiae. Genetics 80(1):23-40
2) Ambroziak J and Henry SA  (1994) INO2 and INO4 gene products, positive regulators of phospholipid biosynthesis in Saccharomyces cerevisiae, form a complex that binds to the INO1 promoter. J Biol Chem 269(21):15344-9
3) Donahue TF and Henry SA  (1981) myo-Inositol-1-phosphate synthase. Characteristics of the enzyme and identification of its structural gene in yeast. J Biol Chem 256(13):7077-85
4) Majumder AL, et al.  (1997) 1L-myo-inositol-1-phosphate synthase. Biochim Biophys Acta 1348(1-2):245-56
5) Griac P and Henry SA  (1999) The yeast inositol-sensitive upstream activating sequence, UASINO, responds to nitrogen availability. Nucleic Acids Res 27(9):2043-50
6) Dean-Johnson M and Henry SA  (1989) Biosynthesis of inositol in yeast. Primary structure of myo-inositol-1-phosphate synthase (EC and functional analysis of its structural gene, the INO1 locus. J Biol Chem 264(2):1274-83
7) Lopes JM, et al.  (1991) Analysis of sequences in the INO1 promoter that are involved in its regulation by phospholipid precursors. Nucleic Acids Res 19(7):1687-93
8) Greenberg ML and Lopes JM  (1996) Genetic regulation of phospholipid biosynthesis in Saccharomyces cerevisiae. Microbiol Rev 60(1):1-20
9) White MJ, et al.  (1991) The OPI1 gene of Saccharomyces cerevisiae, a negative regulator of phospholipid biosynthesis, encodes a protein containing polyglutamine tracts and a leucine zipper. J Biol Chem 266(2):863-72
10) Graves JA and Henry SA  (2000) Regulation of the yeast INO1 gene. The products of the INO2, INO4 and OPI1 regulatory genes are not required for repression in response to inositol. Genetics 154(4):1485-95
11) Sreenivas A, et al.  (2001) Phosphorylation of the yeast phospholipid synthesis regulatory protein Opi1p by protein kinase C. J Biol Chem 276(32):29915-23
12) Scafe C, et al.  (1990) RNA polymerase II mutants defective in transcription of a subset of genes. Mol Cell Biol 10(3):1010-6
13) Shirra MK and Arndt KM  (1999) Evidence for the involvement of the Glc7-Reg1 phosphatase and the Snf1-Snf4 kinase in the regulation of INO1 transcription in Saccharomyces cerevisiae. Genetics 152(1):73-87
14) Peterson CL and Herskowitz I  (1992) Characterization of the yeast SWI1, SWI2, and SWI3 genes, which encode a global activator of transcription. Cell 68(3):573-83