Peptide-templated nucleic acid ligation.

Short oligonucleotide and peptide replicators have been described. To determine whether cross-replication could have occurred between such systems, we have attempted to show that peptides can specifically template the ligation of nucleic acids. A complex between a 35-mer anti-Rev RNA aptamer and a 17-mer arginine-rich motif (ARM) peptide from the HIV-1 Rev protein served as a model system. Aptamer half-molecules were activated for ligation via two activation chemistries, representing two distinct kinetic possibilities for early replicators. Cyanogen bromide activation was transient relative to oligonucleotides that terminated with a 5'-iodine and a 3'phosphorothioate, respectively. The Rev ARM specifically enhanced the degree or rate of ligation by both methods: there was a 10-fold increase in the production of full-length aptamer in the presence of cyanogen bromide and a 5.9- to 7.6-fold enhancement in the rate of ligation for stably activated aptamer half-molecules. These results support the possibility that life could have originated with peptide replicators and transitioned to nucleic acid replicators or that peptide and nucleic acid replicators could have been interdependent.