Telomerase and the Chromosome end Replication Problem

  1. Derek J. Chadwick Organizer and
  2. Gail Cardew Organizer
  1. Thomas R. Cech and
  2. Joachim Lingner

Published Online: 28 SEP 2007

DOI: 10.1002/9780470515433.ch3

Ciba Foundation Symposium 211 - Telomeres and Telomerase

Ciba Foundation Symposium 211 - Telomeres and Telomerase

How to Cite

Cech, T. R. and Lingner, J. (2007) Telomerase and the Chromosome end Replication Problem, in Ciba Foundation Symposium 211 - Telomeres and Telomerase (eds D. J. Chadwick and G. Cardew), John Wiley & Sons, Ltd., Chichester, UK. doi: 10.1002/9780470515433.ch3

Author Information

  1. Howard Hughes Medical Institute, Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309-0215, USA

Publication History

  1. Published Online: 28 SEP 2007

ISBN Information

Print ISBN: 9780471972785

Online ISBN: 9780470515433



  • telomerase rna gene;
  • chromosome end replication problem;
  • DNA length;
  • DNA-protein complex;
  • DNA sequences


Telomerase, the enzyme that extends chromosomal DNA ends in most eukaryotes, contains essential RNA and protein subunits. We have been studying telomere replication in hypotrichous ciliates such as Euplotes aediculatus, which have numerous short macronuclear DNA molecules and therefore are highly enriched in telomeres and in telomerase. Cloning and sequencing genes for the RNA subunits from several ciliates revealed that telomerase RNAs with insignificant nucleotide sequence homology nevertheless form a common secondary structure. Affinity chromatography based on the sequence of the RNA subunit was used to purify the Eupfotes telomerase as an active ribonucleoprotein enzyme. Two protein subunits, 123 kDa and 43 kDa, were identified. The finding of a yeast homologue to the 123 kDa subunit suggests that telomerase protein components may be much more highly conserved in evolution than the RNA subunits. The purified Eujlotei telomerase has no activity with blunt-ended DNA primers, but instead requires a four to six nucleotide single-stranded 3′ tail. This result supports a model for telomere replication in which other activities such as helicases or nucleases activate replicated DNA for extension by telomerase, a model that may be applicable to telomere replication in diverse eukaryotes.