© 2006 Oxford University Press
An unnatural base pair system for in vitro replication and transcription
1 Protein Research Group, RIKEN Genomic Sciences Center, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan, 2 Department of Biophysics and Biochemistry, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan, 3 RIKEN Harima Institute at Spring-8, 1-1-1 Kouto, Mikazuki-cho, Sayo, Hyogo 679-5148, Japan
The development of unnatural base pairs that function in replication, transcription, and translation could expand the genetic alphabet and enable the site-specific incorporation of functional components into nucleic acids and proteins. We present an unnatural base pair between 7-(2-thienyl)-imidazo[4,5-b]pyridine (denoted by Ds) and pyrrole-2-carbaldehyde (denoted by Pa). In replication, the DsPa pair exhibits high selectivity in combination with the usual and modified triphosphate substrates and exonuclease-proficient DNA polymerases. In transcription, the DsPa pair mediates the site-specific incorporation of the substrates of both Ds and Pa into RNA by T7 RNA polymerase. This unnatural base pair system could facilitate the specific incorporation of functional components into RNA molecules at desired positions using DNA templates containing the unnatural base pair, which can be amplified by PCR.