Telomerase is a reverse transcriptase that uses an integral RNA molecule to add de novo G-rich repeats onto telomeric DNA, or onto nontelomeric DNA generated during chromosome fragmentation and breakage events. A telomerase-mediated DNA substrate cleavage activity has been reported in ciliates and yeasts. Nucleolytic cleavage may serve a proofreading function, enhance processivity or ensure that nontemplate telomerase RNA sequences are not copied into DNA. We identified and characterized a human telomerase-mediated nucleolytic cleavage activity using enzyme reconstituted in a rabbit reticulocyte lysate in vitro transcription/translation system and native enzyme extracted from cells. We found that telomerase catalyzed the removal of nucleotides from DNA substrates including those that can form a mismatch with the RNA template or that contain nontelomeric sequences located 3′ to a telomeric sequence. Unlike Tetrahymena telomerase, human telomerase catalyzed the removal of more than one nucleotide (up to 13) from telomeric primers. DNA substrates predicted to align at the 3′-end of the RNA template were not cleaved, consistent with cleavage being dictated by the template 5′-end. We also found some differences in the nuclease activity between RRL-reconstituted human telomerase and native enzyme. © Oxford University Press 2004; all rights reserved.
CITATION STYLE
Huard, S., & Autexier, C. (2004). Human telomerase catalyzes nucleolytic primer cleavage. Nucleic Acids Research, 32(7), 2171–2180. https://doi.org/10.1093/nar/gkh546
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