SOLID-PHASE SYNTHESIS AND RESTRICTION-ENDONUCLEASE CLEAVAGE OF OLIGODEOXYNUCLEOTIDES CONTAINING 5-(HYDROXYMETHYL)-CYTOSINE

Emerging data suggest an important role for cytosine methylation in tu morigenesis. Simultaneously, recent studies indicate a significant con tribution of endogenous oxidative DNA damage to the development of hum an disease. Oxidation of the 5-methyl group of 5-methylcytosine (5(m)C ) residues in DNA results in the formation of 5-(hydroxymethyl)cytosin e (C-hm). The biological consequences of C-hm residues in vertebrate D NA are as yet unknown; however, conversion of the hydrophobic methyl g roup to the hydrophilic hydroxymethyl group may substantially alter th e interaction of sequence-specific binding proteins with DNA, Central to both biophysical and biochemical studies on the potential consequen ces of specific DNA damage products such as C-hm are efficient methods for the synthesis of oligodeoxynucleotides containing such modified b ases at selected positions, In this paper, we describe a method for th e placement of C-hm residues in oligodeoxynucleotides using establishe d phosphoramidite chemistry. In addition, we have examined the influen ce of specific C-hm residues on enzymatic cleavage of oligodeoxynucleo tides by the methylation-sensitive restriction endonucleases Mspl and Hpall.