Tetrahymena telomerase catalyzes nucleolytic cleavage and nonprocessive elongation

Kathleen Collins, Carol W. Greider

Research output: Contribution to journalArticlepeer-review

144 Scopus citations


Telomerase is a ribonucleoprotein enzyme that adds telomeric repeats to chromosomes, maintaining telomere length and stabilizing chromosome ends. In vitro, telomerase from the ciliate Tetrahymena elongates single-stranded, guanosine-rich DNA primers by adding repeats of the Tetrahymena telomeric sequence, dT2G4. We have identified two activities of Tetrahymena telomerase in addition to the previously described processive elongation reaction: a 3′-5′ nucleolytic cleavage of primer or product DNA and a nonprocessive mode of elongation. The nucleolytic cleavage activity removed residues not conforming to the telomeric repeat sequence from a primer 3′ end, eliminating mismatch between DNA primer and RNA template sequences. Template-matched residues were also cleaved from primer or product DNA. Specific primer lengths, sequences, and concentrations stimulated cleavage and processive or nonprocessive elongation differentially. These newly identified activities suggest that telomerase may catalyze a range of telomere synthesis and repair functions and suggest mechanistic similarities between telomerase and RNA polymerase enzymes. On the basis of our results, we propose a model for telomerase primer binding, cleavage, and elongation.

Original languageEnglish (US)
Pages (from-to)1364-1376
Number of pages13
JournalGenes and Development
Issue number7 PART B
StatePublished - Jul 1993
Externally publishedYes


  • Nuclease
  • Polymerase
  • Processivity
  • Telomerase
  • Telomere

ASJC Scopus subject areas

  • General Medicine


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