Evidence for an additional base-pairing element between the telomeric repeat and the telomerase RNA template in Kluyveromyces lactis and other yeasts

Mol Cell Biol. 2009 Oct;29(20):5389-98. doi: 10.1128/MCB.00528-09. Epub 2009 Aug 17.

Abstract

In all telomerases, the template region of the RNA subunit contains a region of telomere homology that is longer than the unit telomeric repeat. This allows a newly synthesized telomeric repeat to translocate back to the 3' end of the template prior to a second round of telomeric repeat synthesis. In the yeast Kluyveromyces lactis, the telomerase RNA (Ter1) template has 30 nucleotides of perfect homology to the 25-bp telomeric repeat. Here we provide strong evidence that three additional nucleotides at positions -2 through -4 present on the 3' side of the template form base-pairing interactions with telomeric DNA. Mutation of these bases can lead to opposite effects on telomere length depending on the sequence permutation of the template in a manner consistent with whether the mutation increases or decreases the base-pairing potential with the telomere. Additionally, mutations in the -2 and -3 positions that restore base-pairing potential can suppress corresponding sequence changes in the telomeric repeat. Finally, multiple other yeast species were found to also have telomerase RNAs that encode relatively long 7- to 10-nucleotide domains predicted to base pair, often with imperfect pairing, with telomeric DNA. We further demonstrate that K. lactis telomeric fragments produce banded patterns with a 25-bp periodicity. This indicates that K. lactis telomeres have preferred termination points within the 25-bp telomeric repeat.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Base Pairing / genetics*
  • Base Pairing / physiology
  • Kluyveromyces / enzymology
  • Kluyveromyces / genetics*
  • RNA / chemistry*
  • RNA / genetics*
  • RNA / metabolism
  • Telomerase / chemistry*
  • Telomerase / genetics*
  • Telomerase / metabolism
  • Telomere / genetics
  • Telomere / physiology*
  • Yeasts / enzymology
  • Yeasts / genetics
  • Yeasts / metabolism

Substances

  • telomerase RNA
  • RNA
  • Telomerase