A template trigger for translocation

Abstract

The telomerase ribonucleoprotein enzyme maintains eukaryotic chromosomes through unique means. Its telomerase reverse transcriptase (TERT) enzymatic subunit synthesizes telomeric DNA repeats from the template RNA subunit (TER) by 'repeat addition processivity'. How telomerase recycles this internal template, and how the template progresses through the TERT active site, was unclear. Berman et al. addressed these questions in Tetrahymena thermophila. They used biochemical assays to assess which regions of TER are important for enzyme activity and assayed changes in RNA conformation during the enzymatic cycle using single molecule fluorescence resonance energy transfer. They propose that the RNA template actively drives translocation through the TERT active site by an 'accordion' movement, in which the RNA sequences that flank the template ensure its correct position and translocation.