CYC8 / YBR112C Overview

Standard Name
CYC8 1
Systematic Name
[OCT1+] 4 , [OCT] , CRT8 29 , SSN6 30
Feature Type
ORF , Verified
Transcriptional regulator; functions primarily as a transcriptional co-repressor with Tup1p but can also function as a transcriptional co-activator with Tup1p that recruits the SWI/SNF and SAGA complexes to promoters; target genes may be uniquely repressed by Cyc8p or Tup1p, subject to redundant repression, or in some cases de-repression of target genes in a cyc8 mutant is dependent upon TUP1 and vice versa; can form the prion [OCT+] 2 3 4 5
Name Description
CYtochrome C 1
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.

CYC8 is located on the right arm of chromosome II between SUS1 transcriptional regulator and RAD16 nucleotide excision repair protein; dubious ORF overlaps 5' end of CYC8 on opposite strand; coding sequence is 2901 nucleotides long with two variable CAA (Q) trinucleotide microsatellites and one variable CAAGCA (QA) microsatellite
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.

Cyc8p is 966 amino acids long, of average half-life, low in abundance; contains variable glutamine repeat near N-terminus, contains variable compound glutamine/alanine repeat near middle of protein; acetylated on 2 lysines, ubiquitinylated on K175, sumoylated on 5 lysines, phosphorylated on 37 residues
Length (a.a.)
Mol. Weight (Da)
Isoelectric Point
Median Abundance (molecules/cell)
5404 +/- 1436
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 CYC8 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-remoding transcription factor that regulates transcription by RNA polymerase II; binds histone deacetylases and is involved in nucleosome positioning; present in transcriptional repressor complex with Tup1p

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 in S288C, essential gene in Sigma1278b; null grows slowly, buds in random pattern, has large rounded cells, short telomeres, decreased lifespan, and cannot respire; null is also sensitive to heat, oxidative stress, metals, acid, and antimalarial drug mefloquine; homozygous diploid null cannot sporulate
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.

Cyc8p interacts physically with proteins involved in transcription; CYC8 interacts genetically with genes involved in transcription

293 total interactions for 193 unique genes

Physical Interactions

  • Affinity Capture-MS: 35
  • Affinity Capture-RNA: 5
  • Affinity Capture-Western: 40
  • Co-fractionation: 2
  • Co-localization: 2
  • PCA: 5
  • Proximity Label-MS: 1
  • Reconstituted Complex: 44
  • Two-hybrid: 16

Genetic Interactions

  • Dosage Rescue: 10
  • Negative Genetic: 87
  • Phenotypic Enhancement: 7
  • Phenotypic Suppression: 7
  • Positive Genetic: 9
  • Synthetic Growth Defect: 3
  • Synthetic Lethality: 3
  • Synthetic Rescue: 17
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.

Cyc8p (also known as Ssn6p) acts with its partner Tup1p as a corepressor to regulate the expression of multiple genes under a variety of conditions. Tup1p-Cyc8p does not bind to DNA directly but is recruited to specific promoters by DNA binding proteins such as Alpha2p, Mig1p, and Crt1p. Evidence suggests that Tup1p-Cyc8p represses transcription by masking and inhibiting the transcriptional activation domains of the recruiting proteins. Tup1p interacts directly with histones H3 and H4, and mutation of these histones synergistically compromises Tup1p-Cyc8p-mediated repression. Histone hyperacetylation caused by combined mutations in genes encoding the histone deacetylases Rpd3p, Hos1p, and Hos2p abolishes repression by Tup1p-Cyc8p. Regulatory regions bound by Tup1p assume a distinct chromatin architecture including nucleosome-depleted regions, poorly positioned promoter nucleosomes and a larger number and wider distribution of accessible transcription factor binding sites. The Tup1p-Cyc8p corepressor complex is composed of one Cyc8p and four Tup1p subunits.
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: 2005-06-28

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.