The ribonucleoprotein telomerase contains two essential components: telomerase RNA (TER) and telomerase reverse transcriptase (TERT, Est2 in yeast). A small portion of TER, termed the template, is copied by TERT onto the chromosome ends, thus compensating for sequence loss due to incomplete DNA replication and nuclease action. Although telomerase RNA is highly divergent in sequence and length across fungi and mammals, structural motifs essential for telomerase function are conserved. Here, we show that Est2 from the budding yeast Kluyveromyces lactis (klEst2) binds specifically to an essential three-way junction (TWJ) structure in K. lactis TER, which shares a conserved structure and sequence features with the essential CR4-CR5 domain of vertebrate telomerase RNA. klEst2 also binds specifically to the template domain, independently and mutually exclusive of its interaction with TWJ. Furthermore, we present the high-resolution structure of the klEst2 telomerase RNA-binding domain (klTRBD). Mutations introduced in vivo in klTRBD based on the solved structure or in TWJ based on its predicted RNA structure caused severe telomere shortening. These results demonstrate the conservation and importance of these domains and the multiple protein–RNA interactions between Est2 and TER for telomerase function.
Bibliographical noteFunding Information:
This work was funded by the United States-Israel Binational Science Foundation [grant numbers 2009204, 2013344] to N.B.U. and Y.T.; Israel Science Foundation grant [2071/18] to Y.T.; National Cancer Institute [RO1 CA201312-01] to E.S.; The Wistar Cancer Center Support Grant [P30 CA10815] to E.S.; and a short-term fellowship by the European Molecular Biology Organization to Y.B.
© 2022 by the authors.
- crystal structure
- telomerase RNA
- three-way junction