Laura Landweber

Department of Ecology and Evolutionary Biology
Princeton University

Comparison of a representative region of the COIII mRNA sequences with the corresponding regions of the mitochondrial DNA. Hm, H. mariadeanei; Tb, T. brucei; Lt, L. tarentolae, Cf, C. fasciculata. DNA sequences in upper case; u's are uridines in mRNA that are added by RNA editing; encoded thymidines deleted from the mRNA indicated by gaps. In boxes are conserved nucleotides that are frameshifted by editing.

In vitro selection, or directed molecular evolution, allows the isolation and amplification of rare sequences that satisfy a selection criterion. This technique can be used to isolate novel ribozymes (RNA enzymes) from large pools of random sequence. We have recently used in vitro evolution to discover a ribozyme that catalyzes a novel template-directed RNA ligation. This reaction is unusual in its preference for extensive base-pairing and the requirement only 28 selected nucleotides for activity. Our results suggest that similar small RNA ligase motifs can arise under fairly simple conditions, which could have led to the production of longer and more complex RNA polymers in prebiotic evolution.

Other experiments I will describe survey the natural diversity of genetic systems to draw inferences about which processes are primitive or derived. These include RNA editing and gene scrambling, two forms of genetic information processing which take place in kinetoplastid and ciliated protozoa, respectively.

Thursday, May 15, 1997 at 4pm in Room 317 the Towne Building, located at 220 South 33rd Street at the University of Pennsylvania.