Addition of short guanylyl blocks to oligonucleotide primers with a thermophilic polynucleotide phosphorylase. Its application to the synthesis of oligonucleotides containing guanylyl residues.

Polynucleotide phosphorylase from Thermus thermophilus catalyzed the addition of short guanylyl blocks from GDP to the 3'-hydroxyl termini of oligonucleotide primers at low temperature in a simple reaction mixture. Polyguanylic acid formation was inhibited at 37 degrees C, but the addition of one or two guanylyl residues to oligonucleotide primers proceeded in high yields. The reaction was applied to the synthesis of oligonucleotides containing guanylyl residues at the 3'-end. Using (Ap)2A and (Up)2U as primers, (Ap)3G, (Ap)3GpG, and (Up)3G were synthesized in yields of 25--52%. (Ap)2GpG was synthesized from ApA and GDP in a yield of 13%.