SIR3 / YLR442C Overview

Standard Name
SIR3 1
Systematic Name
CMT1 30 , MAR2 31 32 , STE8 33
Feature Type
ORF , Verified
Silencing protein; interacts with Sir2p, Sir4p, and histone H3/H4 tails to establish transcriptionally silent chromatin; required for spreading of silenced chromatin; recruited to chromatin through interaction with Rap1p; C-terminus assumes variant winged helix-turn-helix (wH) fold that mediates homodimerization, which is critical for holo-SIR complex loading; required for telomere hypercluster formation in quiescent yeast cells; has paralog ORC1 from whole genome duplication 1 2 3 4 5 6 7
Name Description
Silent Information Regulator 1
ORC1 5
Comparative Info
Sequence Details


The S. cerevisiae Reference Genome sequence is derived from laboratory strain S288C. Download DNA or protein sequence, view genomic context and coordinates. Click "Sequence Details" to view all sequence information for this locus, including that for other strains.

SIR3 has a paralog, ORC1, that arose from the whole genome duplication
Protein Details


Basic sequence-derived (length, molecular weight, isoelectric point) and experimentally-determined (median abundance, median absolute deviation) protein information. Click "Protein Details" for further information about the protein such as half-life, abundance, domains, domains shared with other proteins, protein sequence retrieval for various strains, physico-chemical properties, protein modification sites, and external identifiers for the protein.

Length (a.a.)
Mol. Weight (Da)
Isoelectric Point
Median Abundance (molecules/cell)
1453 +/- 938
Half-life (hr)


Curated mutant alleles for the specified gene, listed alphabetically. Click on the allele name to open the allele page. Click "SGD search" to view all alleles in search results. Click "YeastMine" to view all alleles in YeastMine.

View all SIR3 alleles in SGD search | YeastMine

Gene Ontology Details

Gene Ontology

GO Annotations consist of four mandatory components: a gene product, a term from one of the three Gene Ontology (GO) controlled vocabularies (Molecular Function, Biological Process, and Cellular Component), a reference, and an evidence code. SGD has manually curated and high-throughput GO Annotations, both derived from the literature, as well as computational, or predicted, annotations. Click "Gene Ontology Details" to view all GO information and evidence for this locus as well as biological processes it shares with other genes.

Chromatin- and DNA-binding protein involved heterochromatin formation, telomere tethering, double-strand break repair via nonhomologous end joining, and negative regulation of DNA replication; localizes to telomeres, nucleolus, and mitochondria; subunit of chromatin silencing complex

View computational annotations

Molecular Function

Manually Curated

Cellular Component

Manually Curated


Macromolecular complex annotations are imported from the Complex Portal. These annotations have been derived from physical molecular interaction evidence extracted from the literature and cross-referenced in the entry, or by curator inference from information on homologs in closely related species or by inference from scientific background.

Phenotype Details


Phenotype annotations for a gene are curated single mutant phenotypes that require an observable (e.g., "cell shape"), a qualifier (e.g., "abnormal"), a mutant type (e.g., null), strain background, and a reference. In addition, annotations are classified as classical genetics or high-throughput (e.g., large scale survey, systematic mutation set). Whenever possible, allele information and additional details are provided. Click "Phenotype Details" to view all phenotype annotations and evidence for this locus as well as phenotypes it shares with other genes.

Non-essential gene; null mutant has reduced replicative lifespan and is pheromone-unresponsive; conditional mutant is sterile, unable to shmoo, or arrest the cell cycle in the presence of pheromone and produces very low levels of mating pheromone; conditional mutant has a bipolar budding pattern like diploids; haploinsufficiency in the heterozygous null mutant is associated with elevated chromosomal instability; homozygous diploid null mutant has abnormal meiosis with delayed centromere clustering, bouquet formation, homologue pairing, and meiotic divisions; overexpression results in a decreased growth rate
Interaction Details


Interaction annotations are curated by BioGRID and include physical or genetic interactions observed between at least two genes. An interaction annotation is composed of the interaction type, name of the interactor, assay type (e.g., Two-Hybrid), annotation type (e.g., manual or high-throughput), and a reference, as well as other experimental details. Click "Interaction Details" to view all interaction annotations and evidence for this locus, including an interaction visualization.

The sir3 null mutant is viable; the null mutant of paralog orc1 is inviable; the sir3 orc1 double mutant has not been annotated for phenotype.

332 total interactions for 125 unique genes

Physical Interactions

  • Affinity Capture-MS: 43
  • Affinity Capture-RNA: 5
  • Affinity Capture-Western: 50
  • Biochemical Activity: 4
  • Co-crystal Structure: 2
  • Co-fractionation: 1
  • Co-localization: 10
  • Co-purification: 2
  • Cross-Linking-MS (XL-MS): 1
  • Far Western: 2
  • Protein-peptide: 4
  • Reconstituted Complex: 53
  • Two-hybrid: 30

Genetic Interactions

  • Dosage Growth Defect: 1
  • Dosage Lethality: 1
  • Dosage Rescue: 13
  • Negative Genetic: 3
  • Phenotypic Enhancement: 14
  • Phenotypic Suppression: 25
  • Positive Genetic: 1
  • Synthetic Growth Defect: 18
  • Synthetic Lethality: 1
  • Synthetic Rescue: 48
Regulation Details


The number of putative Regulators (genes that regulate it) and Targets (genes it regulates) for the given locus, based on experimental evidence. This evidence includes data generated through high-throughput techniques. Click "Regulation Details" to view all regulation annotations, shared GO enrichment among regulation Targets, and a regulator/target diagram for the locus.

Expression Details


Expression data are derived from records contained in the Gene Expression Omnibus (GEO), and are first log2 transformed and normalized. Referenced datasets may contain one or more condition(s), and as a result there may be a greater number of conditions than datasets represented in a single clickable histogram bar. The histogram division at 0.0 separates the down-regulated (green) conditions and datasets from those that are up-regulated (red). Click "Expression Details" to view all expression annotations and details for this locus, including a visualization of genes that share a similar expression pattern.

Summary Paragraph

A summary of the locus, written by SGD Biocurators following a thorough review of the literature. Links to gene names and curated GO terms are included within the Summary Paragraphs.

Last Updated: 1999-09-01

Literature Details


All manually curated literature for the specified gene, organized into topics according to their relevance to the gene (Primary Literature, Additional Literature, or Review). Click "Literature Details" to view all literature information for this locus, including shared literature between genes.