CYC7/YEL039C Summary Help

Standard Name CYC7
Systematic Name YEL039C
Feature Type ORF, Verified
Description Cytochrome c isoform 2, expressed under hypoxic conditions; electron carrier of the mitochondrial intermembrane space that transfers electrons from ubiquinone-cytochrome c oxidoreductase to cytochrome c oxidase during cellular respiration; protein abundance increases in response to DNA replication stress; CYC7 has a paralog, CYC1, that arose from the whole genome duplication (1, 2, 3, 4 and see Summary Paragraph)
Name Description CYtochrome C
Gene Product Alias iso-2-cytochrome c 2
Chromosomal Location
ChrV:79977 to 79636 | ORF Map | GBrowse
Note: this feature is encoded on the Crick strand.
Genetic position: -27 cM
Gene Ontology Annotations All CYC7 GO evidence and references
  View Computational GO annotations for CYC7
Molecular Function
Manually curated
Biological Process
Manually curated
Cellular Component
Manually curated
Regulators 7 genes
Classical genetics
Large-scale survey
23 total interaction(s) for 22 unique genes/features.
Physical Interactions
  • Affinity Capture-MS: 6
  • Affinity Capture-RNA: 1
  • Biochemical Activity: 4
  • PCA: 3
  • Protein-RNA: 1
  • Reconstituted Complex: 1

Genetic Interactions
  • Dosage Rescue: 1
  • Negative Genetic: 1
  • Phenotypic Enhancement: 1
  • Phenotypic Suppression: 1
  • Synthetic Growth Defect: 2
  • Synthetic Lethality: 1

Expression Summary
Length (a.a.) 113
Molecular Weight (Da) 12,532
Isoelectric Point (pI) 10.4
Phosphorylation PhosphoGRID | PhosphoPep Database
sequence information
ChrV:79977 to 79636 | ORF Map | GBrowse
Note: this feature is encoded on the Crick strand.
Genetic position: -27 cM
Last Update Coordinates: 1996-07-31 | Sequence: 1996-07-31
Subfeature details
Most Recent Updates
Coordinates Sequence
CDS 1..342 79977..79636 1996-07-31 1996-07-31
Retrieve sequences
Analyze Sequence
S288C only
S288C vs. other species
S288C vs. other strains
External Links All Associated Seq | Entrez Gene | Entrez RefSeq Protein | MIPS | Search all NCBI (Entrez) | UniProtKB
Primary SGDIDS000000765

CYC7 encodes an isoform, known as iso-2, of the electron carrier protein cytochrome c (5). Cytochrome c facilitates the penultimate and last steps of the mitochondrial respiratory chain via its covalently attached heme group: electron transfer from respiratory complex III to respiratory complex IV, and the final transfer of electrons to oxygen catalyzed by complex IV, cytochrome c oxidase. The cytochrome c genes were among the first yeast genes to be identified and have been studied extensively (6, 2, 7; reviewed in 8).

Transcription of CYC7 is repressed under aerobic conditions and induced at low oxygen concentrations (1, 9). Repression under aerobic conditions is mediated by the transcriptional repressor Rox1p (10); CYC7 is additionally subject to carbon catabolite repression (11). The CYC7 promoter contains a binding site for direct transcriptional activation by Hap1p in the presence of heme (12, 13, 14, 11).

Cyc7p comprises about 5% of the cytochrome c present in cells grown under aerobic, non-glucose repressing conditions, while the major isoform, Cyc1p, comprises 95% (6); the two isoforms are 84% identical to each other at the protein sequence level. Unlike iso-1 cytochrome c (Cyc1p), the Cyc7p apopotein (lacking its heme moiety) is not subject to degradation by the ubiquitin-dependent protein degradation pathway (15). Similar to Cyc1p, however, a single lysine residue of apo-Cyc7p is trimethylated in the cytoplasm by the action of the cytochrome c-specific methyltransferase Ctm1p (16, 17). Cyc7p is imported into the mitochondrial intermembrane space by a mechanism requiring the outer membrane translocase (TOM) complex (18, 19). Once in the intermembrane space, Cyc7p is covalently attached to heme in a reaction catalyzed by cytochrome c heme lyase (Cyc3p) (20).

Last updated: 2007-08-01 Contact SGD

References cited on this page View Complete Literature Guide for CYC7
1) Burke PV, et al.  (1997) Effects of oxygen concentration on the expression of cytochrome c and cytochrome c oxidase genes in yeast. J Biol Chem 272(23):14705-12
2) Downie JA, et al.  (1977) Structural gene for yeast iso-2-cytochrome c. J Mol Biol 113(2):369-84
3) Byrne KP and Wolfe KH  (2005) The Yeast Gene Order Browser: combining curated homology and syntenic context reveals gene fate in polyploid species. Genome Res 15(10):1456-61
4) Tkach JM, et al.  (2012) Dissecting DNA damage response pathways by analysing protein localization and abundance changes during DNA replication stress. Nat Cell Biol 14(9):966-76
5) Montgomery DL, et al.  (1980) Isolation and sequence of the gene for iso-2-cytochrome c in Saccharomyces cerevisiae. Proc Natl Acad Sci U S A 77(1):541-5
6) Sherman F, et al.  (1965) Genetic determination of iso-cytochromes c in yeast. J Mol Biol 13(1):21-39
7) Sherman F  (1990) Studies of yeast cytochrome c: how and why they started and why they continued. Genetics 125(1):9-12
8) Sherman F  (2005) The importance of mutation, then and now: studies with yeast cytochrome c. Mutat Res 589(1):1-16
9) Kwast KE, et al.  (1999) Oxygen sensing in yeast: evidence for the involvement of the respiratory chain in regulating the transcription of a subset of hypoxic genes. Proc Natl Acad Sci U S A 96(10):5446-51
10) Lowry CV and Zitomer RS  (1988) ROX1 encodes a heme-induced repression factor regulating ANB1 and CYC7 of Saccharomyces cerevisiae. Mol Cell Biol 8(11):4651-8
11) Prezant T, et al.  (1987) Organization of the regulatory region of the yeast CYC7 gene: multiple factors are involved in regulation. Mol Cell Biol 7(9):3252-9
12) Wright CF and Zitomer RS  (1984) A positive regulatory site and a negative regulatory site control the expression of the Saccharomyces cerevisiae CYC7 gene. Mol Cell Biol 4(10):2023-30
13) Verdiere J, et al.  (1985) Regulation of the expression of iso 2-cytochrome c gene in S. cerevisiae: cloning of the positive regulatory gene CYP1 and identification of the region of its target sequence on the structural gene CYP3. Mol Gen Genet 199(3):524-33
14) Fytlovich S, et al.  (1993) Evidence for an interaction between the CYP1(HAP1) activator and a cellular factor during heme-dependent transcriptional regulation in the yeast Saccharomyces cerevisiae. EMBO J 12(3):1209-18
15) Pearce DA and Sherman F  (1997) Differential ubiquitin-dependent degradation of the yeast apo-cytochrome c isozymes. J Biol Chem 272(50):31829-36
16) DeLange RJ, et al.  (1970) Identification and location of episilon-N-trimethyllysine in yeast cytochromes c. J Biol Chem 245(13):3325-7
17) Polevoda B, et al.  (2000) Cytochrome c methyltransferase, Ctm1p, of yeast. J Biol Chem 275(27):20508-13
18) Diekert K, et al.  (2001) Apocytochrome c requires the TOM complex for translocation across the mitochondrial outer membrane. EMBO J 20(20):5626-35
19) Wiedemann N, et al.  (2003) Biogenesis of yeast mitochondrial cytochrome c: a unique relationship to the TOM machinery. J Mol Biol 327(2):465-74
20) Wang X, et al.  (1996) Sequence requirements for mitochondrial import of yeast cytochrome c. J Biol Chem 271(12):6594-604