DNA methylation: sequences flanking C-G pairs modulate the specificity of the human DNA methylase.

AUTOR(ES)

Bolden, A H

RESUMO

Synthetic single-stranded oligodeoxynucleotides of known sequence have been used as in vitro substrates for a partially purified HeLa cell DNA methylase. Although most oligonucleotides tested cannot be used by the HeLa DNA methylase in vitro, we have found a unique 27mer, containing 2 C-G pairs, that is an excellent substrate for the enzyme. Analysis of the methylation of the 27mer, its derivatives and other oligomer substrates reveal that the HeLa DNA methylase does not significantly methylate an oligomer which contains just one C-G pair. In addition, only one of the two C-G pairs in the 27mer is methylated and this methylation is abolished if the other C-G pair is converted to a C-A pair. Furthermore, the HeLa enzyme apparently cannot methylate C-G pairs located in compounds containing a high A + T content. The most efficient methylation occurs with multiple separated C-G pairs in a compound with a high G + C content (greater than 65%). The results suggest that clustering of C-G pairs in regions of the DNA high in G + C content may be the preferred site for DNA methylation in vivo.

Documentos Relacionados

• The sequence specificity of a mammalian DNA methylase.
• In vitro methylation of DNA with Hpa II methylase.
• DNA methylation pattern is determined by the intracellular level of the methylase.
• Flanking sequences modulate the cell specificity of M-CAT elements.
• The role of the preserved sequences of Dam methylase.