Details

Autor(en) / Beteiligte

• Christman, Judith K.
• Sheikhnejad, Gholamreza
• Marasco, Canio J.
• Sufrin, Janice R.

Titel

5-Methyl-2'-Deoxycytidine in Single-Stranded DNA Can Act in Cis to Signal De novo DNA Methylation

Ist Teil von

• Proceedings of the National Academy of Sciences - PNAS, 1995-08, Vol.92 (16), p.7347-7351

Ort / Verlag

United States: National Academy of Sciences of the United States of America

Erscheinungsjahr

1995

Quelle

EZB-FREE-00999 freely available EZB journals

Beschreibungen/Notizen

• Methylation of cytosine residues in DNA plays an important role in regulating gene expression during vertebrate embryonic development. Conversely, disruption of normal patterns of methylation is common in tumors and occurs early in progression of some human cancers. In vertebrates, it appears that the same DNA methyltransferase maintains preexisting patterns of methylation during DNA replication and carries out de novo methylation to create new methylation patterns. There are several indications that inherent signals in DNA structure can act in vivo to initiate or block de novo methylation in adjacent DNA regions. To identify sequences capable of enhancing de novo methylation of DNA in vitro, we designed a series of oligodeoxyribonucleotide substrates with substrate cytosine residues in different sequence contexts. We obtained evidence that some 5-methylcytosine residues in these single-stranded DNAs can stimulate de novo methylation of adjacent sites by murine DNA 5-cytosine methyltransferase as effectively as 5-methylcytosine residues in double-stranded DNA stimulate maintenance methylation. This suggests that double-stranded DNA may not be the primary natural substrate for de novo methylation and that looped single-stranded structures formed during the normal course of DNA replication or repair serve as "nucleation" sites for de novo methylation of adjacent DNA regions.