Bacillus subtilis alkA gene encoding inducible 3-methyladenine DNA glycosylase is adjacent to the ada operon.
In Bacillus subtilis, the adaptive response to DNA alkylation depends on the ada operon, which consists of the adaA and adaB genes, which encode methylphosphotriester DNA methyltransferase (AdaA protein) and O6-methylguanine DNA methyltransferase (AdaB protein), respectively. A structural gene (alkA) that encodes 3-methyladenine DNA glycosylase was found upstream of the ada operon, but in the opposite orientation. This cluster of genes was mapped at about 235 kb from the SfiI recognition site near the origin of replication in the physical map of the B. subtilis chromosome. Disruption of the alkA gene sensitized cells to N-propyl-N'-nitro-N-nitrosoguanidine, while its overproduction rendered cells highly resistant to N-propyl-N'-nitro-N-nitrosoguanidine, indicating that lethal DNA damage produced by bulky alkylating agents was effectively counteracted by AlkA glycosylase. Transcription of the alkA gene was induced by treating adaA+ cells with methylating agents concurrent with transcription of the ada operon. This was accomplished by using methylated AdaA protein bound to a 30-bp segment in the middle of the 100-bp sequence between the transcriptional start sites of the alkA gene and ada operon. Thus, in this organism, the adaptive response to DNA alkylation is achieved by autologous activation of a divergent regulon composed of the genes for a DNA glycosylase and two species of DNA alkyltransferase.
Radiobiology Division, National Cancer Center Research Institute, Tokyo, Japan.
F
F
Morohoshi
K
K
Hayashi
N
N
Munkata
D000477:Alkylating Agents / Q000494:pharmacology; D000478:Alkylation; D000595:Amino Acid Sequence; D001412:Bacillus subtilis / Q000201:enzymology / Q000235:genetics*; D001426:Bacterial Proteins / Q000235:genetics; D001483:Base Sequence; D003001:Cloning, Molecular; D045647:DNA Glycosylases; D004260:DNA Repair; D004269:DNA, Bacterial; D003850:Deoxyribonuclease I; D004790:Enzyme Induction; D004926:Escherichia coli; D029968:Escherichia coli Proteins; D008780:Methyltransferases / Q000235:genetics; D008969:Molecular Sequence Data; D009699:N-Glycosyl Hydrolases / Q000096:biosynthesis / Q000235:genetics*; D019853:O(6)-Methylguanine-DNA Methyltransferase; D016366:Open Reading Frames; D009876:Operon; D015183:Restriction Mapping; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors
D000477:Alkylating Agents; D001426:Bacterial Proteins; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D014157:Transcription Factors; D008780:Methyltransferases; C045666:methylphosphotriester methyltransferase; C045675:Ada protein, E coli; D019853:O(6)-Methylguanine-DNA Methyltransferase; D003850:Deoxyribonuclease I; C021565:3-methyladenine-DNA glycosylase; D045647:DNA Glycosylases; D009699:N-Glycosyl Hydrolases