The response of M.HpaII to heteroduplexes.
Synthetic oligodeoxyribonucleotide duplexes have been used to study the methylation specificity of M.HpaII, a bacterial DNA methyltransferase. Substrates of four types were compared. A 30-mer containing a Watson-Crick paired CCGG recognition sequence was rapidly methylated at the central cytosine on each strand in the recognition sequence. A 30-mer containing an asymmetrically methylated recognition sequence, of the type transiently produced by DNA replication, was rapidly methylated at the central cytosine on the unmethylated strand. A heteroduplex containing an A.C mispair in the recognition sequence (CCGG/CCAG) was rapidly methylated at the cytosine in the mispair. A heteroduplex containing an A.C and an adjacent C.C mispair in the recognition sequence (CCGG/CCCA) was not methylated at a significant rate. The results show that M.HpaII can tolerate a single mispair at its recognition site in a heteroduplex without loss of activity or specificity.
Department of Cell and Tumor Biology, City of Hope Medical Center, Duarte, CA 91010.
A
A
Laayoun
D J
DJ
Baker
J
J
Riley
S S
SS
Smith
D015257:DNA-Cytosine Methylases / Q000378:metabolism*; D008745:Methylation; D009692:Nucleic Acid Heteroduplexes / Q000378:metabolism*; D009838:Oligodeoxyribonucleotides / Q000378:metabolism; D013379:Substrate Specificity
D009692:Nucleic Acid Heteroduplexes; D009838:Oligodeoxyribonucleotides; C029641:DNA modification methylase HpaII; D015257:DNA-Cytosine Methylases