SPECIFIC TELOMERASE RNA RESIDUES DISTANT FROM THE TEMPLATE ARE ESSENTIAL FOR TELOMERASE FUNCTION

The reverse transcriptase telomerase is a ribonucleoprotein complex th at adds telomeric repeats to chromosome ends, using a sequence within its endogenous RNA component as a template. Although templating domain s of telomerase RNA have been studied in detail, little is known about the roles of the remaining residues, particularly in yeast. We examin ed the functions of nontemplate telomerase residues in the telomerase RNA of budding yeast Kluyveromyces lactis. Although approximately half of the RNA residues were dispensable for function, four specific regi ons were essential for telomerase action in vivo. We analyzed the effe cts of mutating these regions on in vivo function, in vitro telomerase activity, and telomerase RNP assembly. Deletion of two regions result ed in synthesis of stable RNAs that appeared unable to assemble into a stable RNP. Mutating a region near the 5' end of the RNA allowed RNP assembly but abolished enzymatic activity. Mutations in another specif ic small region of the RNA led to an inactive telomerase RNP with an a ltered RNA conformation.