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Molecular and Cellular Biology, October 2009, p. 5389-5398, Vol. 29, No. 20
0270-7306/09/$08.00+0     doi:10.1128/MCB.00528-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Evidence for an Additional Base-Pairing Element between the Telomeric Repeat and the Telomerase RNA Template in Kluyveromyces lactis and Other Yeasts{triangledown}

Zhi-Ru Wang,{dagger} Leilei Guo, Lizhen Chen,{ddagger} and Michael J. McEachern*

Department of Genetics, Fred Davison Life Science Complex, University of Georgia, Athens, Georgia 30602-7223

Received 23 April 2009/ Returned for modification 8 June 2009/ Accepted 7 August 2009

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.

* Corresponding author. Mailing address: Department of Genetics, Davison Life Sciences Building, University of Georgia, Athens, GA 30602. Phone: (706) 542-1821. Fax: (706) 542-3910. E-mail: mjm{at}uga.edu

{triangledown} Published ahead of print on 17 August 2009.

{dagger} Present address: Department of Surgery, Second Hospital, Shanxi Medical University, Taiyuan, Shanxi 030001, China.

{ddagger} Present address: Department of Biology, University of California San Diego, La Jolla, CA 92093.

Molecular and Cellular Biology, October 2009, p. 5389-5398, Vol. 29, No. 20
0270-7306/09/$08.00+0     doi:10.1128/MCB.00528-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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