Nonenzymatic ligation of short-chained 2′-5′- or 3′-5′-linked oligoribonucleotides on 2′-5′- or 3′-5′-linked complementary templates

5'-pACUG tetraribonucleotides containing 2'-5' or 3'-5' linkages I self-condensed on 2'-5'- or 3'-5'-linked complementary decariboi-nucleotide (5'-CAGUCAGUCA) templates. CD and UV melting studies showed that helix formation took place in all four possible combinations of linkage isomers of the substrate tetramer and the template decamer under the ligation conditions. The hybridization ability followed the order: [3'-5' tetramer with 3'-5' decomer] > [2'-5' tetramer with 3'-5' decamer] > [2'-5' tetramer with 2'-5' decamer] > [3'-5' tetramer with 2'-5' decamer]. Each tetramer condensed on the complementary decaribonucletide template to form the corresponding octamer, but the ligation efficiency varied considerably, depending on the types of linkage in the tetramer substrate and the template decamer. The yields of the octamers obtained by the template-directed ligation followed the order: [2'-5' substrate: 2'-5'template] > [3'-5':3'-5'] > [2'-5':3'-5'] > [3'-5'.-2'-5']. The results demonstrate that a homo-linkage system is preferable for the template-directed synthesis of RNA. The resulting linkage of the octamer formed from the 2'-5'-linked substrate and the 2'-5'-linked template is mainly 2'-5'.