A triple helix within a pseudoknot is a conserved and essential element of telomerase RNA

Kinneret Shefer, Yogev Brown, Valentin Gorkovoy, Tamar Nussbaum, Nikolai B. Ulyanov*, Yehuda Tzfati

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

67 Scopus citations


Telomerase copies a short template within its integral telomerase RNA onto eukaryotic chromosome ends, compensating for incomplete replication and degradation. Telomerase action extends the proliferative potential of cells, and thus it is implicated in cancer and aging. Nontemplate regions of telomerase RNA are also crucial for telomerase function. However, they are highly divergent in sequence among species, and their roles are largely unclear. Using in silico three-dimensional modeling, constrained by mutational analysis, we propose a three-dimensional model for a pseudoknot in telomerase RNA of the budding yeast Kluyveromyces lactis. Interestingly, this structure includes a U-A · U major-groove triple helix. We confirmed the triple-helix formation in vitro using oligoribonucleotides and showed that it is essential for telomerase function in vivo. While triplex-disrupting mutations abolished telomerase function, triple compensatory mutations that formed pH-dependent G-C · C+ triples restored the pseudoknot structure in a pH-dependent manner and partly restored telomerase function in vivo. In addition, we identified a novel type of triple helix that is formed by G-C · U triples, which also partly restored the pseudoknot structure and function. We propose that this unusual structure, so far found only in telomerase RNA, provides an essential and conserved telomerase-specific function.

Original languageAmerican English
Pages (from-to)2130-2143
Number of pages14
JournalMolecular and Cellular Biology
Issue number6
StatePublished - Mar 2007


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