title: A versatile endonuclease IV from Thermus thermophilus has uracil-excising and 3'-5' exonuclease activity.
abstract: Apurinic/apyrimidinic (AP) sites arise in DNA through the spontaneous loss of bases or through the release of damaged bases from DNA by DNA glycosylases. AP sites in DNA can be catalyzed by AP endonucleases such as exonuclease III and endonuclease IV, generating a 3'-hydroxyl group and a 5'-terminal sugar phosphate. Here, we have identified and characterized a novel endonuclease IV from a hyperthermophilic bacterium Thermus thermophilus designated as TthNfo. TthNfo efficiently removed AP site from double-stranded oligonucleotide substrate. No significant difference was observed in the rate of reaction of four bases opposite AP site with TthNfo. In addition, TthNfo possesses a 3'-5' exonuclease activity similar to that of Escherichia coli exonuclease III. Surprisingly, we found that TthNfo also catalyzes the excision of uracil from DNA. In comparison with other endonuclease IV proteins, the removal of uracil residue was unique to TthNfo. Based on these observations and the absence of exonuclease III in T. thermophilus, we suggest that versatile enzyme activities of TthNfo play an important role in counteracting DNA base damage in vivo.
authors.affiliation: Department of Advanced Technology Fusion, BMIC, Konkuk University, Seoul 143-701, Republic of Korea.
authors.forename: Jung Ho
authors.initials: JH
authors.lastname: Back
authors.forename: Ji Hyung
authors.initials: JH
authors.lastname: Chung
authors.forename: Jong Hwa
authors.initials: JH
authors.lastname: Park
authors.forename: Ye Sun
authors.initials: YS
authors.lastname: Han
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D017124:Conserved Sequence; D004247:DNA / Q000378:metabolism; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase / Q000378:metabolism; D043223:Deoxyribonuclease IV (Phage T4-Induced) / Q000737:chemistry / Q000145:classification / Q000302:isolation & purification / Q000378:metabolism*; D005092:Exonucleases / Q000737:chemistry / Q000145:classification / Q000302:isolation & purification / Q000378:metabolism*; D008969:Molecular Sequence Data; D016415:Sequence Alignment; D013379:Substrate Specificity; D016963:Thermus thermophilus / Q000201:enzymology*; D014498:Uracil / Q000378:metabolism*
chemical_list: D014498:Uracil; D004247:DNA; D005092:Exonucleases; D043223:Deoxyribonuclease IV (Phage T4-Induced); D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase