title: Escherichia coli apurinic-apyrimidinic endonucleases enhance the turnover of the adenine glycosylase MutY with G:A substrates.
abstract: The DNA repair enzyme MutY plays an important role in the prevention of DNA mutations resulting from the presence of the oxidatively damaged lesion 7,8-dihydro-8-oxo-2'-deoxyguanosine (OG). MutY is a base excision repair (BER) glycosylase that removes misincorporated adenine residues from OG:A mispairs, as well as G:A and C:A mispairs. We have previously shown that, under conditions of low MutY concentrations relative to an OG:A or G:A substrate, the time course of the adenine glycosylase reaction exhibits biphasic kinetic behavior due to slow release of the DNA product by MutY. The dissociation of MutY from its product may require the recruitment of other proteins from the BER pathway, such as an apurinic-apyrimidinic (AP) endonuclease, as turnover-enhancing cofactors. The effect of the AP endonucleases endonuclease IV (Endo IV), exonuclease III (Exo III), and Ape1 on the reaction kinetics of MutY with G:A- and OG:A-containing substrates was investigated. The effect of the glycosylases UDG and MutM and the DNA polymerase pol I was also characterized. Endo IV and Exo III, unlike Ape1, UDG, and pol I, greatly enhance the rate of product release with a G:A substrate, whereas the rate constant for the adenine removal step remains unchanged. Furthermore, the turnover rate with a truncated form of MutY, Stop 225, which lacks 125 amino acids of the C terminus, is unaffected by the presence of Endo IV or Exo III. These results constitute the first evidence of an interaction between the MutY-product DNA complex and Endo IV or Exo III. Furthermore, they suggest a role for the C-terminal domain of MutY in mediating this interaction.
authors.affiliation: Department of Chemistry, University of Utah, Salt Lake City, Utah 84103, USA.
authors.forename: Mary Ann
authors.initials: MA
authors.lastname: Pope
authors.forename: Silvia L
authors.initials: SL
authors.lastname: Porello
authors.forename: Sheila S
authors.initials: SS
authors.lastname: David
mesh_terms: D000080242:8-Hydroxy-2'-Deoxyguanosine; D019757:Carbon-Oxygen Lyases / Q000737:chemistry* / Q000378:metabolism*; D004247:DNA / Q000378:metabolism; D045647:DNA Glycosylases; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase; D043382:DNA-Formamidopyrimidine Glycosylase; D003849:Deoxyguanosine / Q000031:analogs & derivatives / Q000378:metabolism; D043223:Deoxyribonuclease IV (Phage T4-Induced); D004706:Endodeoxyribonucleases / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology*; D029968:Escherichia coli Proteins; D005090:Exodeoxyribonucleases / Q000378:metabolism; D007700:Kinetics; D008956:Models, Chemical; D009699:N-Glycosyl Hydrolases / Q000235:genetics / Q000378:metabolism*; D009841:Oligonucleotides / Q000737:chemistry; D010957:Plasmids / Q000378:metabolism; D017434:Protein Structure, Tertiary; D013997:Time Factors
chemical_list: D029968:Escherichia coli Proteins; D009841:Oligonucleotides; D000080242:8-Hydroxy-2'-Deoxyguanosine; D004247:DNA; D004706:Endodeoxyribonucleases; D005090:Exodeoxyribonucleases; C020133:exodeoxyribonuclease III; D043223:Deoxyribonuclease IV (Phage T4-Induced); C468972:endonuclease IV, E coli; D045647:DNA Glycosylases; D009699:N-Glycosyl Hydrolases; C437225:adenine glycosylase; C061738:mutY adenine glycosylase; D043382:DNA-Formamidopyrimidine Glycosylase; C468610:DNA-formamidopyrimidine glycosylase, E coli; D019757:Carbon-Oxygen Lyases; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase; D003849:Deoxyguanosine