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In DNA repair, the Ada Regulon is a set of genes whose expression is essential to adaptive response (also known as "Ada response", hence the name), which is triggered in prokaryotic cells by exposure to sub-lethal doses of alkylating agents. This allows the cells to tolerate the effects of such agents, which are otherwise toxic and mutagenic. The Ada response includes the expression of four genes: ''ada, alkA, alkB, and aidB''. The product of ''ada'' gene, the Ada protein, is an activator of transcription of all four genes. DNA bases damaged by alkylation are removed by distinct strategies. == Alkylating agents == The alkylating agents from a group of mutagens and carcinogens that modify DNA by alkylation. Alkyl base lesions can arrest replication, interrupt transcription, or signal the activation of cell cycle checkpoints or apoptosis. In mammals, they could be involved in carcinogenesis, neurodegenerative disease and aging. The alkylating agents can introduce methyl or ethyl groups at all of the available nitrogen and oxygen atoms in DNA bases, providing a number of lesions. The majority of evidence indicates that among the 11 identified base modification two, 3-methyladenine (3meA) and O6-methylguanine (O6-meG), are mainly responsible for the biological effects of alkylation agents.〔Singer B (1976) All oxygens in nucleic acids react with carcinogenic ethylating agents. ''Nature'' 264: 333–339〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Ada regulon」の詳細全文を読む スポンサード リンク
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