Differential subcellular localization of human MutY homolog (hMYH) and the functional activity of adenine:8-oxoguanine DNA glycosylase.
The post-replicative adenine:8-oxo-7,8-dihydroguanine (GO) mismatch is crucial for G:C to T:A transversion. This mismatch is corrected by Escherichia coli MutY which excises the adenine from A:GO. A candidate gene coding for the human counterpart of MutY has been cloned as hMYH. However, the function and enzyme activities of the gene product have not been identified. We previously demonstrated that an epitope-tagged hMYH protein behaves as a mitochondrial protein. In the present study, we have identified an alternative hMYH transcript, termed type 2, which differs in the exon 1 sequence of the known transcript (type 1). A nuclear localization for the type 2 protein was revealed by detection of epitope-tagged protein in COS-7 cells. Expression of both type 1 and type 2 transcripts was reduced in post-mitotic tissues. hMYH cDNA suppressed the mutator phenotype of E.coli mutY. In vitro expressed hMYH showed adenine DNA glycosylase activity toward the A:GO substrate. The protein can bind to A:GO, and to T:GO and G:GO without apparent catalysis. These results represent the first demonstration of the function of the hMYH gene product which is differentially transported into the nucleus or the mitochondria by alternative splicing
Takao
M
M
Department of Molecular Genetics, Institute of Development, Aging and Cancer, Tohoku University, 4-1 Seiryo-machi, Aoba-ku, Sendai 980-8578, Japan. mtakao@idac.tohoku.ac.jp
Zhang
Q M
QM
Yonei
S
S
Yasui
A
A
D000225:Adenine / Q000378:metabolism*; D017398:Alternative Splicing; D000818:Animals; D020137:Base Pair Mismatch / Q000235:genetics*; D001692:Biological Transport; D019556:COS Cells; D002384:Catalysis; D002467:Cell Nucleus / Q000201:enzymology*; D045647:DNA Glycosylases; D004260:DNA Repair / Q000235:genetics; D043382:DNA-Formamidopyrimidine Glycosylase; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D029968:Escherichia coli Proteins; D005091:Exons / Q000235:genetics; D006147:Guanine / Q000378:metabolism; D006801:Humans; D007527:Isoenzymes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D009699:N-Glycosyl Hydrolases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010641:Phenotype; D012333:RNA, Messenger / Q000032:analysis / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013489:Suppression, Genetic / Q000235:genetics; D013941:Thymine / Q000378:metabolism
D029968:Escherichia coli Proteins; D007527:Isoenzymes; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D006147:Guanine; D045647:DNA Glycosylases; D009699:N-Glycosyl Hydrolases; C061738:mutY adenine glycosylase; D043382:DNA-Formamidopyrimidine Glycosylase; C468610:DNA-formamidopyrimidine glycosylase, E coli; D000225:Adenine; D013941:Thymine