Disease relevance of ada

• The ada and aidB genes are part of the adaptive response to DNA methylation damage in Escherichia coli [1].
• We have used a replication-incompetent retrovirus to transfer into mammalian cells a chimeric gene consisting of 548 bp of the promoter-regulatory region of the gene for P-enolpyruvate carboxykinase (GTP) (EC 4.1.1.32) (PEPCK) linked to ada [2].
• Pretreatment of bacterial host (including the ada- mutant) with low doses of alkylating agents increases the survival of MMS (but not HA)-treated phages; pretreatment of bacteria with HA has no effect on survival of HA-treated phages [3].
• The importance of DNA repair, shown by reversal of damage and attenuation of the toxicity of CLB and PAM, was indicated by the susceptibility of cells lacking O(6)-methylguanine-DNA methyltransferase I and II (ada ogt) [4].

High impact information on ada

• Transcription of the ada and the aidB genes is triggered by binding of the methylated Ada protein (meAda) to a specific sequence located 40-60 base pairs upstream of the transcriptional start, which is internal to an A/T-rich region [1].
• The ada-specific RNA was produced when the Ada protein treated with methyl methanesulfonate or with methyl iodide was present in the reaction mixture [5].
• In this process Ada protein, the product of the ada gene, plays a major role; it accepts the methyl groups of the methylated DNA at the cysteine residues of its own molecule, and the methylated form of Ada protein promotes transcription of its own gene, thereby triggering induction of the whole process [5].
• To investigate the potential of DNA repair proteins to reduce bone marrow sensitivity to the CENUs, we transferred the Escherichia coli ada gene, which encodes a Mr 39,000 O6-alkylguanine-DNA alkyltransferase (ATase), into murine bone marrow cells by the use of a high-titer ecotropic retrovirus [6].
• The ada-encoded ATase is resistant to O6-benzylguanine (O6-BG), a potent inhibitor of the mammalian ATases, thus affording the bone marrow an additional level of protection against CENUs [6].

Chemical compound and disease context of ada

• Transfection of the Escherichia coli ada gene coding for O6-alkylguanine-DNA alkyltransferase results in expression of ada in mammalian cells and transmission of nitrosourea resistance to cells lacking alkyltransferase activity [2].
• Except for the insensitivity to methyl methanesulfonate, the phenotypes of these mutants look very similar to those of ada mutants isolated previously in Escherichia coli [7].
• The plasmids were isolated from plasmid stocks carrying total cellular DNA by selection for their ability to complement the methylmethanesulphonate(MMS)-sensitive phenotype of an E. coli mutant (tag ada) deficient in both 3-methyladenine DNA glycosylases I and II [8].

Biological context of ada

• Although a number of peptide domains are conserved between the E. coli 39 kDa ada protein and phosphates can also be used to explain the observed sequence specific repair of this lesion within certain DNA sequences [9].
• Thus, retroviral gene transfer of the PEPCKada chimeric gene allows efficient and inducible expression of ada with a resulting increase in alkyltransferase activity and nitrosourea drug resistance [2].
• The ada mutations have been shown to map in the 47 to 53-min region of the E. coli chromosome [10].

Anatomical context of ada

• In methylcellulose cultures, ada-infected hematopoietic progenitor cells were twice as resistant as uninfected cells to the toxic effects of 1, 3-bis(2-chloroethyl)-1-nitrosourea (BCNU) following treatment with O6-BG [6].

Associations of ada with chemical compounds

• NRK clones expressing ada had up to 2.0-fold increased resistance to 1,3-bis(2- chloroethyl)-1- nitrosourea [2].
• Transcription of ada mRNA originating from the PEPCK promoter was induced with Bt2cAMP or dexamethasone and the combination caused a 4-fold increase in ada mRNA while total alkyltransferase activity was induced up to 2-fold [2].

Analytical, diagnostic and therapeutic context of ada

• These results suggest that ada gene therapy may be a feasible approach to amelioration of delayed myelosuppression following O6-BG plus CENU combination chemotherapy [6].

References