Telomerase: an RNP enzyme synthesizes DNA.

TLDR: The underlying conservation of a core set of structural features of telomerase RNAs important for the fundamental polymerase activity of telomersase are described, which include a pseudoknot-plus-template domain and at least one other RNA structural motif separate from the template-containing domain.

Abstract: SUMMARY Telomerase is a eukaryotic ribonucleoprotein (RNP) whose specialized reverse transcriptase action performs de novo synthesis of one strand of telomeric DNA. The resulting telomerase-mediated elongation of telomeres, which are the protective end-caps for eukaryotic chromosomes, counterbalances the inevitable attrition from incomplete DNA replication and nucleaseaction.Thetelomerasestrategytomaintaintelomeresisdeeplyconservedamongeukaryotes, yet the RNA component of telomerase, which carries the built-in template for telomeric DNA repeat synthesis, has evolutionarily diverse size and sequence. Telomerase shows adistributionoflaborbetweenRNAandproteininaspectsofthepolymerizationreaction.This article first describesthe underlying conservation of acore set of structural features of telomerase RNAs important for the fundamental polymerase activity of telomerase. These include a pseudoknot-plus-template domain and at least one other RNA structural motif separate from the template-containing domain. The principles driving the diversity of telomerase RNAs are then explored. Much of the diversification of telomerase RNAs has come from apparent gain-of-function elaborations, through inferred evolutionaryacquisitions of various RNA motifs used for telomerase RNP biogenesis, cellular trafficking of enzyme components, and regulation of telomerase action at telomeres. Telomerase offers broadly applicable insights into the interplay of protein and RNA functions in the context of an RNP enzyme.