"Repair of 3-methylthymine and 1-methylguanine lesions by bacterial and
human AlkB proteins."
The Escherichia coli AlkB protein repairs 1-methyladenine (1-meA) and
3-methylcytosine (3-meC) lesions in DNA and RNA by oxidative
demethylation, a reaction requiring ferrous iron and 2-oxoglutarate as
cofactor and co-substrate, respectively. Here, we have studied the
activity of AlkB proteins on 3-methylthymine (3-meT) and 1-methylguanine
(1-meG), two minor lesions which are structurally analogous to 1-meA and
3-meC. AlkB as well as the human AlkB homologues, hABH2 and hABH3, were
all able to demethylate 3-meT in a DNA oligonucleotide containing a single
3-meT residue. Also, 1-meG lesions introduced by chemical methylation of
tRNA were efficiently removed by AlkB. Unlike 1-meA and 3-meC, nucleosides
or bases corresponding to 1-meG or 3-meT did not stimulate the uncoupled,
AlkB-mediated decarboxylation of 2-oxoglutarate. Our data show that 3-meT
and 1-meG are repaired by AlkB, but indicate that the recognition of these
substrates is different from that in the case of 1-meA and 3-meC.
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Last modification of this entry: Sept. 3, 2009
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