APN2/YBL019W Summary Help

Standard Name APN2 1
Systematic Name YBL019W
Alias ETH1 2
Feature Type ORF, Verified
Description Class II abasic (AP) endonuclease involved in repair of DNA damage; homolog of human HAP1 and E. coli exoIII (1, 3 and see Summary Paragraph)
Name Description APurinic/apyrimidinic eNdonuclease 1
Chromosomal Location
ChrII:184353 to 185915 | ORF Map | GBrowse
Gene Ontology Annotations All APN2 GO evidence and references
Molecular Function
Manually curated
Biological Process
Manually curated
Cellular Component
Manually curated
Regulators 1 genes
Classical genetics
Large-scale survey
72 total interaction(s) for 39 unique genes/features.
Physical Interactions
  • Affinity Capture-MS: 2
  • Co-purification: 1
  • Two-hybrid: 2

Genetic Interactions
  • Dosage Rescue: 1
  • Negative Genetic: 4
  • Phenotypic Enhancement: 18
  • Phenotypic Suppression: 5
  • Positive Genetic: 1
  • Synthetic Growth Defect: 18
  • Synthetic Lethality: 16
  • Synthetic Rescue: 4

Expression Summary
Length (a.a.) 520
Molecular Weight (Da) 59,445
Isoelectric Point (pI) 9.81
Phosphorylation PhosphoGRID | PhosphoPep Database
sequence information
ChrII:184353 to 185915 | ORF Map | GBrowse
Last Update Coordinates: 2011-02-03 | Sequence: 1997-01-28
Subfeature details
Most Recent Updates
Coordinates Sequence
CDS 1..1563 184353..185915 2011-02-03 1997-01-28
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 SGDIDS000000115

APN1 and APN2 encode multi-functional enzymes involved in the repair of damaged bases in DNA (reviewed in 4 and 5). Both Apn1p and Apn2p possess an apurinic/apyrimidinic (AP) endonuclease activity, a 3'-diesterase activity, and a 3' to 5' exonuclease activity (6, 7, 3). However, Apn1p constitutes the major apurinic/apyrimidinic (AP) endonuclease and 3'-phosphodiesterase in vivo, constituting close to 97% of these activities (6). During base excision repair (BER), the AP-endonuclease activity nicks the 5' side of abasic sites that are generated by the removal of oxidized and alkylated bases. This creates a single-strand break that contains a 3' hydroxyl group in preparation for DNA synthesis (8, 3). The 3'-phosphodiesterase activity is able to remove a wide range of 3' moieties at end of single-strand breaks in order to generate a 3' hydroxyl group (9, 7). The 3' to 5' exonuclease activity removes single nucleotides at a nick, such as 8oxodGMP that is mispaired with adenine/cytosine, leaving a single-nucleotide gap (10, 11, 7).

APN2 represents an alternate pathway for the repair of abasic sites. Although the methyl-methane sulfonate (MMS) sensitivity of apn2 single mutant strains are similar to wild-type strains, an apn1 apn2 double mutant is extremely sensitive (1). APN2 expression is induced six-fold in response to MMS (2).

Apn2p has sequence similarity to E. coli exonuclease III, S. pombe Apn2, and human Ape1 and Ape2 (1, 3, 12).

Last updated: 2006-10-26 Contact SGD

References cited on this page View Complete Literature Guide for APN2
1) Johnson RE, et al.  (1998) Identification of APN2, the Saccharomyces cerevisiae homolog of the major human AP endonuclease HAP1, and its role in the repair of abasic sites. Genes Dev 12(19):3137-43
2) Bennett RA  (1999) The Saccharomyces cerevisiae ETH1 gene, an inducible homolog of exonuclease III that provides resistance to DNA-damaging agents and limits spontaneous mutagenesis. Mol Cell Biol 19(3):1800-9
3) Unk I, et al.  (2000) Apurinic endonuclease activity of yeast Apn2 protein. J Biol Chem 275(29):22427-34
4) Boiteux S and Guillet M  (2004) Abasic sites in DNA: repair and biological consequences in Saccharomyces cerevisiae. DNA Repair (Amst) 3(1):1-12
5) Ramotar D  (1997) The apurinic-apyrimidinic endonuclease IV family of DNA repair enzymes. Biochem Cell Biol 75(4):327-36
6) Popoff SC, et al.  (1990) Yeast structural gene (APN1) for the major apurinic endonuclease: homology to Escherichia coli endonuclease IV. Proc Natl Acad Sci U S A 87(11):4193-7
7) Unk I, et al.  (2001) 3'-phosphodiesterase and 3'-->5' exonuclease activities of yeast Apn2 protein and requirement of these activities for repair of oxidative DNA damage. Mol Cell Biol 21(5):1656-61
8) Johnson AW and Demple B  (1988) Yeast DNA 3'-repair diesterase is the major cellular apurinic/apyrimidinic endonuclease: substrate specificity and kinetics. J Biol Chem 263(34):18017-22
9) Johnson AW and Demple B  (1988) Yeast DNA diesterase for 3'-fragments of deoxyribose: purification and physical properties of a repair enzyme for oxidative DNA damage. J Biol Chem 263(34):18009-16
10) Ishchenko AA, et al.  (2005) The 3'->5' exonuclease of Apn1 provides an alternative pathway to repair 7,8-dihydro-8-oxodeoxyguanosine in Saccharomyces cerevisiae. Mol Cell Biol 25(15):6380-90
11) Vance JR and Wilson TE  (2001) Repair of DNA strand breaks by the overlapping functions of lesion-specific and non-lesion-specific DNA 3' phosphatases. Mol Cell Biol 21(21):7191-8
12) Shatilla A, et al.  (2005) Identification of two apurinic/apyrimidinic endonucleases from Caenorhabditis elegans by cross-species complementation. DNA Repair (Amst) 4(6):655-70