title: The cytosine N4-methyltransferase M.PvuII also modifies adenine residues.
abstract: Methylation of DNA occurs at the C5 and N4 positions of cytosine and N6 of adenine. The chemistry of methylation is similar among methyltransferases specific for cytosine-N4 and adenine-N6. Moreover these enzymes have similar structures and active sites. Previously it has been demonstrated that the DNA-(adenine-N6)-methyltransferases M.EcoRV, M.EcoRI, E. coli dam and both domains of M.FokI also modify cytosine residues at the N4 position [Jeltsch et al., J. Biol. Chem. 274 (1999), 19538-19544]. Here we show that the cytosine-N4 methyltransferase M.PvuII, which modifies the second cytosine in CAGCTG sequences, also methylates adenine residues in CAGATG/CAGCTG substrates in which the target cytosine is replaced by adenine in one strand of the recognition sequence. Therefore, adenine-N6 and cytosine-N4 methyltransferases have overlapping target base specificities. These results demonstrate that the target base recognition by N-specific DNA methyltransferases is relaxed in many cases. Furthermore, it shows that the catalytic mechanisms of adenine-N6 and cytosine-N4 methyltransferases are very similar.
authors.affiliation: Institut für Biochemie, Fachbereich 8, Justus-Liebig-Universität, Giessen, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Jeltsch
mesh_terms: D000225:Adenine / Q000378:metabolism*; D001665:Binding Sites; D002384:Catalysis; D003596:Cytosine / Q000378:metabolism*; D019175:DNA Methylation; D015257:DNA-Cytosine Methylases / Q000378:metabolism*; D015265:Site-Specific DNA-Methyltransferase (Adenine-Specific) / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D003596:Cytosine; D015257:DNA-Cytosine Methylases; D015265:Site-Specific DNA-Methyltransferase (Adenine-Specific); D000225:Adenine