The Effects of Relocating the Ku-binding Stem-loop of Telomerase RNA on Telomere Healing Events

Abstract

In most eukaryotes, the enzyme telomerase adds telomeric DNA repeats to the 3' ends of chromosomes in order to stabilize them and protect them from degradation. In the budding yeast Saccharomyces cerevisiae, telomerase is a ribonucleoprotein complex consisting of multiple protein subunits and an approximately 1.3 kb RNA component termed TLC1. Among the various proteins involved in telomerase, Ku is a heterodimer that binds both to double-stranded DNA and to a 48 nucleotide stem loop on the TLC1 RNA. Beyond its function of extending telomeres at the ends of chromosomes, telomerase can also be instrumental in repairing double-stranded DNA breaks (DSBs) by adding telomeric repeats at the site of the break. This stabilizes the damaged chromosome, but also silences genes proximal to the break. Ku is an important factor in the recruitment of telomerase to these double stranded breaks, so this investigation explored whether TLC1 structural variants with relocated Ku-binding sites are still capable of healing chromosomes via the addition of telomeres. It was determined that the TLC1 RNA is flexible and can retain its function with relocated and additional Ku-binding stem loops.