title: Evidence for an additional base-pairing element between the telomeric repeat and the telomerase RNA template in Kluyveromyces lactis and other yeasts.
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.
authors.affiliation: Department of Genetics, Davison Life Sciences Building, University of Georgia, Athens, GA 30602, USA.
authors.forename: Zhi-Ru
authors.initials: ZR
authors.lastname: Wang
authors.forename: Leilei
authors.initials: L
authors.lastname: Guo
authors.forename: Lizhen
authors.initials: L
authors.lastname: Chen
authors.forename: Michael J
authors.initials: MJ
authors.lastname: McEachern
mesh_terms: D020029:Base Pairing / Q000235:genetics* / Q000502:physiology; D007716:Kluyveromyces / Q000201:enzymology / Q000235:genetics*; D012313:RNA / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D019098:Telomerase / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D016615:Telomere / Q000235:genetics / Q000502:physiology*; D015003:Yeasts / Q000201:enzymology / Q000235:genetics / Q000378:metabolism
chemical_list: C422952:telomerase RNA; D012313:RNA; D019098:Telomerase
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