title: An O6-methylguanine-DNA methyltransferase-like protein from Thermus thermophilus interacts with a nucleotide excision repair protein.
abstract: The major damage to DNA caused by alkylating agents involves the formation of O6-methylguanine (O6-meG). Almost all species possess O6-methylguanine-DNA-methyltransferase (Ogt) to repair such damage. Ogt repairs O6-meG lesions in DNA by stoichiometric transfer of the methyl group to a cysteine residue in its active site (PCHR). Thermus thermophilus HB8 has an Ogt homologue, TTHA1564, but in this case an alanine residue replaces cysteine in the putative active site. To reveal the possible function of TTHA1564 in processing O6-meG-containing DNA, we characterized the biochemical properties of TTHA1564. No methyltransferase activity for synthetic O6-meG-containing DNA could be detected, indicating TTHA1564 is an alkyltransferase-like protein. Nevertheless, gel shift assays showed that TTHA1564 can bind to DNA containing O6-meG with higher affinity (9-fold) than normal (unmethylated) DNA. Experiments using a fluorescent oligonucleotide suggested that TTHA1564 recognizes O6-meG in DNA using the same mechanism as other Ogts. We then investigated whether TTHA1564 functions as a damage sensor. Pull-down assays identified 20 proteins, including a nucleotide excision repair protein UvrA, which interacts with TTHA1564. Interaction of TTHA1564 with UvrA was confirmed using a surface plasmon resonance assay. These results suggest the possible involvement of TTHA1564 in DNA repair pathways.
authors.affiliation: Department of Biological Sciences, Graduate School of Science, Osaka University, 1-1 Machikaneyama-cho, Toyonaka, Osaka 560-0043, Japan.
authors.forename: Rihito
authors.initials: R
authors.lastname: Morita
authors.forename: Noriko
authors.initials: N
authors.lastname: Nakagawa
authors.forename: Seiki
authors.initials: S
authors.lastname: Kuramitsu
authors.forename: Ryoji
authors.initials: R
authors.lastname: Masui
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004247:DNA / Q000737:chemistry / Q000378:metabolism; D004260:DNA Repair; D045643:DNA Repair Enzymes / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D006147:Guanine / Q000031:analogs & derivatives / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D019853:O(6)-Methylguanine-DNA Methyltransferase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D016963:Thermus thermophilus / Q000201:enzymology*
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D006147:Guanine; D004247:DNA; C008449:O-(6)-methylguanine; D019853:O(6)-Methylguanine-DNA Methyltransferase; D045643:DNA Repair Enzymes