Szostak of Massachusetts General Hospital, Boston, devised the approach, which is based on messenger RNA (mRNA) display and in vitro selection (Nature 2007, 448, 828). mRNA display generates very large libraries of proteins covalently linked to their encoding mRNAs, and in vitro selection is an iterative, cyclic way to screen molecules for desired properties. Using mRNA display, Seelig and Szostak generated a library of more than 1012 randomized "zinc finger" proteins, which are known to bind nucleic acids. To each mRNA-protein conjugate, they attached complementary DNA and an RNA substrate. Then they exposed the resulting structures to another RNA substrate bearing an anchor group. When an mRNA-protein conjugate catalyzed ligation of the RNA substrates, it could be isolated because it bound to a bead through the anchor group. The DNA for each "hit" was amplified (or mutated and amplified) and added to the library to enrich it for further selection cycles until an enzyme with unique RNA ligase activity was identified.
by Stu Borman |
August 20, 2007