Forms and Functions of Telomerase RNA

Abstract

Telomerase adds single-stranded telomeric DNA repeats to chromosome ends. Unlike other polymerases involved in genome replication, telomerase synthe¬sizes DNA without use of a DNA template. Instead, the enzyme active site copies a template carried within the integral RNA subunit of the telomerase ribonucleo-protein (RNP) complex. In addition to providing a template, telomerase RNA has non-template motifs with critical functions in the catalytic cycle of repeat synthesis. In its complexity of structure and function, telomerase RNA resembles the non-coding RNAs of RNP machines like the ribosome and spliceosome that evolved from catalytic RNAs of the RNA World. However, unlike these RNPs, telomerase evolved its RNP identity after advent of the Protein World. Insights about telomer-ase have broad significance for understanding non-coding RNA biology as well as chromosome end maintenance and human disease.