210 Hornby- Notes
- Methylated DNA does not transform as efficiently as unmodified DNA
into a number of common strains of E. coli. In general, strain C600 is
suitable for Me-CG-modified DNA, RR1 for Me-CC modification, and
K803 can tolerate both. This problem arises owing to the action of the
mcrA mcrB genes of E. coli, which lead to restriction of cytosine-modified
DNA. A detailed account of this problem has been given by Raleigh (2). - 5-d-Azacytidine, when incorporated into DNA, is a potent inhibitor of
the Mtase reaction. It !s thought that the analog traps the covalent enzyme-
SH:pyridine intermediate, since methyltransfer to the 5-N position is
mechanistically improbable (6).The peptide methinin is another potent
inhibitor of mammalian DNA Mtase activity. However, its mode of
action is obscure.
Acknowledgments
I would like to thank all of the members of my laboratory for their
helpful comments on the manuscript.
Abbreviations
Mtase, methyltransferase; SAM, S-adenosylmethionine; dA,
deoxyadenine; dC, deoxycytidine; N, any deoxynucleotide; p, phosphate;
Me, methyl; SAH, S-adenosylhomocysteine; dam-, DNA adenine methy-
lation; ATP, adenosine triphosphate; HPLC, High-performance liquid chro-
matography; Py, pyrimidine; Pu, purine.
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deoxycytidines in human DNA are not in the CpG dinucleotide. Biochem.
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