Single-step elongation of oligodeoxynucleotides using terminal deoxynucleotidyl transferase

Procedures for the stepwise addition of one or more deoxyribonucleotide residues to the 3' end of an oligodeoxyribonucleoside phosphate acceptor using commercially available terminal deoxynucleotidyl transferase is described. 2-80 nmol of acceptors with a chain length of four, five or nine monomer units were elongated with a single 2'-deoxyribonucleoside 5'-triphosphate in yields of 20-30%. The monomers carried no protecting groups and were used both radioactively labelled and unlabelled. The elongated oligodeoxynucleoside phosphates were isolated by reverse-phase (Nucleosil C18) high-performance liquid chromatography or paper chromatography. The isolated products were sequenced by the fingerprint method. Advantages and disadvantages of this new methodology for the enzymatic synthesis of defined oligodeoxynucleotides are discussed.