Expression and differential intracellular localization of two major forms of human 8-oxoguanine DNA glycosylase encoded by alternatively spliced OGG1 mRNAs.
We identified seven alternatively spliced forms of human 8-oxoguanine DNA glycosylase (OGG1) mRNAs, classified into two types based on their last exons (type 1 with exon 7: 1a and 1b; type 2 with exon 8: 2a to 2e). Types 1a and 2a mRNAs are major in human tissues. Seven mRNAs are expected to encode different polypeptides (OGG1-1a to 2e) that share their N terminus with the common mitochondrial targeting signal, and each possesses a unique C terminus. A 36-kDa polypeptide, corresponding to OGG1-1a recognized only by antibodies against the region containing helix-hairpin-helix-PVD motif, was copurified from the nuclear extract with an activity introducing a nick into DNA containing 8-oxoguanine. A 40-kDa polypeptide corresponding to a processed form of OGG1-2a was detected in their mitochondria using antibodies against its C terminus. Electron microscopic immunocytochemistry and subfractionation of the mitochondria revealed that OGG1-2a locates on the inner membrane of mitochondria. Deletion mutant analyses revealed that the unique C terminus of OGG1-2a and its mitochondrial targeting signal are essential for mitochondrial localization and that nuclear localization of OGG1-1a depends on the NLS at its C terminus.
Nishioka
K
K
Department of Biochemistry, Medical Institute of Bioregulation, Kyushu University, Fukuoka 812-8582, Japan.
Ohtsubo
T
T
Oda
H
H
Fujiwara
T
T
Kang
D
D
Sugimachi
K
K
Nakabeppu
Y
Y
D017398:Alternative Splicing; D000595:Amino Acid Sequence; D001483:Base Sequence; D002467:Cell Nucleus / Q000201:enzymology; D043382:DNA-Formamidopyrimidine Glycosylase; D006801:Humans; D007425:Intracellular Membranes / Q000201:enzymology; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D008928:Mitochondria / Q000201:enzymology / Q000648:ultrastructure; D008969:Molecular Sequence Data; D009699:N-Glycosyl Hydrolases / Q000032:analysis / Q000235:genetics* / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction
D007527:Isoenzymes; D012333:RNA, Messenger; D011994:Recombinant Proteins; D009699:N-Glycosyl Hydrolases; D043382:DNA-Formamidopyrimidine Glycosylase