Telomerase RNA Shapes the Evolutionary Diversity of Telomerase Ribonucleoproteins (RNPs)

Telomerase emerged in early eukaryotes as a highly specialized reverse transcriptase for maintaining chromosome integrity. The telomerase enzyme contains an integral RNA, providing the template for DNA repeat synthesis. This central telomerase RNA not only provides the template but also contributes to the enzyme's catalytic function and the biogenesis of the ribonucleoprotein. Remarkably, telomerase RNA exhibits significant diversity in sequence, structure, and biogenesis across eukaryotic lineages, a feature that sets it apart from other functional RNAs. In ciliates and plants, telomerase RNA is transcribed by RNA polymerase III, whereas in animals and fungi, it is predominantly transcribed by RNA polymerase II. These differences result in distinct pathways for RNA synthesis, maturation, and trafficking. This work highlights how the diversity in size and structure of telomerase RNAs impacts the complexity and evolution of telomerase ribonucleoproteins, spanning from unicellular eukaryotes to multicellular plants and animals, highlighting telomerase RNA's critical role in telomere biology.