Mammalian 5-formyluracil-DNA glycosylase. 2. Role of SMUG1 uracil-DNA glycosylase in repair of 5-formyluracil and other oxidized and deaminated base lesions.
In the accompanying paper [Matsubara, M., et al. (2003) Biochemistry 42, 4993-5002], we have partially purified and characterized rat 5-formyluracil (fU)-DNA glycosylase (FDG). Several lines of evidence have indicated that FDG is a rat homologue of single-strand-selective monofunctional uracil-DNA glycosylase (SMUG1). We report here that rat and human SMUG1 (rSMUG1 and hSMUG1) expressed from the corresponding cDNAs indeed excise fU in single-stranded (ss) and double-stranded (ds) DNA. The enzymes also excised uracil (U) and uracil derivatives bearing an oxidized group at C5 [5-hydroxyuracil (hoU) and 5-hydroxymethyluracil (hmU)] in ssDNA and dsDNA but not analogous cytosine derivatives (5-hydroxycytosine and 5-formylcytosine) and other oxidized damage. The damage specificity and the salt concentration dependence of rSMUG1 (and hSMUG1) agreed well with those of FDG, confirming that FDG is rSMUG1. Consistent with the damage specificity above, hSMUG1 removed damaged bases from Fenton-oxidized calf thymus DNA, generating abasic sites. The amount of resulting abasic sites was about 10% of that generated by endonuclease III or 8-oxoguanine glycosylase in the same substrate. The HeLa cell extract and hSMUG1 exhibited a similar damage preference (hoU.G > hmU.A, fU.A), and the activities for fU, hmU, and hoU in the cell extract were effectively neutralized with hSMUG1 antibodies. These data indicate a dual role of hSMUG1 as a backup enzyme for UNG and a primary repair enzyme for a subset of oxidized pyrimidines such as fU, hmU, and hoU.
Masaoka
Aya
A
Department of Mathematical and Life Sciences, Graduate School of Science, Hiroshima University, Higashi-Hiroshima 739-8526, Japan.
Matsubara
Mayumi
M
Hasegawa
Rei
R
Tanaka
Tamon
T
Kurisu
Satofumi
S
Terato
Hiroaki
H
Ohyama
Yoshihiko
Y
Karino
Naoko
N
Matsuda
Akira
A
Ide
Hiroshi
H
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D017124:Conserved Sequence; D004249:DNA Damage; D045647:DNA Glycosylases; D017931:DNA Primers; D004260:DNA Repair; D004277:DNA, Single-Stranded / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D009699:N-Glycosyl Hydrolases / Q000737:chemistry / Q000378:metabolism*; D010084:Oxidation-Reduction; D051381:Rats; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D014498:Uracil / Q000031:analogs & derivatives* / Q000378:metabolism*; D051981:Uracil-DNA Glycosidase
D017931:DNA Primers; D004277:DNA, Single-Stranded; C007777:5-formyluracil; D014498:Uracil; D045647:DNA Glycosylases; D009699:N-Glycosyl Hydrolases; C498095:SMUG1 protein, human; D051981:Uracil-DNA Glycosidase