Synthesis of Oligonucleotide Inhibitors of DNA (Cytosine-C5) Methyltransferase Containing 5-Azacytosine Residues at Specific Sites

Abstract

The incorporation of 5-azacytosine residues into DNA causes potent inhibition of DNA (Cytosine-C5) methyl-transferases. The synthesis of oligodeoxyribonucleotides incorporating single or multiple 5-aza-2 ′-deoxycytidine residues at precise sites was undertaken to generate an array of sequences containing the reactive 5-aza-cytosine base as specific target sites for enzymatic methylation. Preparation of these modified oligonucleotides requires the use of 2-(p-nitrophenyl)ethyloxycarbonyl (NPEOC) groups for the protection of exocyclic amino functions. These groups are removed under mild conditions, thus avoiding conventional protocols that are detrimental to the integrity of the 5-azacytosine ring.