Origin-Of-Life Implications For Synthetic RNA …

Motivated by the idea that RNA may have been life’s first chemical machinery, scientists have developed RNA molecules that can synthesize new RNAs up to about 95 nucleotides in length or that can assemble a new RNA that is itself an active enzyme (Science, DOI: 10.1126/science.1200752). The earliest denizens of a primitive “RNA world” might have been RNA molecules with the ability to self-replicate. In their hunt for such molecules, Philipp Holliger and colleagues at the Medical Research Council Laboratory of Molecular Biology, in Cambridge, England, used a previously engineered RNA called R18 as a starting point. Until now, R18 was only capable of assembling RNAs about 20 nucleotides long, but the Cambridge team’s screen, which selects for RNAs that can string many nucleotides together, helped them design improved RNA enzymes. These next-generation RNAs can’t make copies of themselves, and their yields of long RNAs are limited. Still, the work “is very exciting,” says Ronald R. Breaker, who studies RNA function at Yale University. “The authors have pushed an RNA to the brink of self-replication—just a bit farther and no more nudges will be needed.”