DNA Nucleotidylexotransferase

Publication Title: 
Nucleic Acids Research

The ribonucleoprotein enzyme telomerase is a specialized type of cellular reverse transcriptase which synthesizes one strand of telomeric DNA, using as the template a sequence in the RNA moiety of telomerase. We analyzed the effects of various nucleoside analogs, known to be chain-terminating inhibitors of retroviral reverse transcriptases, on Tetrahymena thermophila telomerase activity in vitro. We also analyzed the effects of such analogs on telomere length and maintenance in vivo, and on vegetative growth and mating of Tetrahymena cells.

Author(s): 
Strahl, C.
Blackburn, E. H.
Publication Title: 
Science (New York, N.Y.)

The ribonucleoprotein enzyme telomerase synthesizes telomeric DNA by copying an internal RNA template sequence. The telomerase activities of the yeasts Saccharomyces castellii and Saccharomyces cerevisiae--with regular and irregular telomeric sequences, respectively--have now been identified and characterized. The S. cerevisiae activity required the telomerase RNA gene TLC1 but not the EST1 gene, both of which are required for normal telomere maintenance in vivo. This activity exhibited low processivity and produced no regularly repeated products.

Author(s): 
Cohn, M.
Blackburn, E. H.
Publication Title: 
Cold Spring Harbor Symposia on Quantitative Biology
Author(s): 
Lee, M. S.
Gallagher, R. C.
Bradley, J.
Blackburn, E. H.
Publication Title: 
Proceedings of the National Academy of Sciences of the United States of America

Macronuclear telomeres in Oxytricha exist as DNA-protein complexes in which the termini of the G-rich strands are bound by a 97-kDa telomere protein. During telomeric DNA replication, the replication machinery must have access to the G-rich strand. However, given the stability of telomere protein binding, it has been unclear how this is accomplished. In this study we investigated the ability of several different DNA polymerases to access telomeric DNA in Oxytricha telomere protein-DNA complexes.

Author(s): 
Shippen, D. E.
Blackburn, E. H.
Price, C. M.
Publication Title: 
Cell

We have analyzed the de novo telomere synthesis catalyzed by the enzyme telomere terminal transferase (telomerase) from Tetrahymena. Oligonucleotides representing the G-rich strand of telomeric sequences from five different organisms specifically primed the addition of TTGGGG repeats in vitro, suggesting that primer recognition may involve a DNA structure unique to these oligonucleotides. The sequence at the 3' end of the oligonucleotide primer specified the first nucleotide added in the reaction.

Author(s): 
Greider, C. W.
Blackburn, E. H.
Publication Title: 
Science (New York, N.Y.)

The RNA moiety of the ribonucleoprotein enzyme telomerase from the ciliate Euplotes crassus was identified and its gene was sequenced. Functional analysis, in which oligonucleotides complementary to portions of the telomerase RNA were tested for their ability to prime telomerase in vitro, showed that the sequence 5' CAAAACCCCAAA 3' in this RNA is the template for synthesis of telomeric TTTTGGGG repeats by the Euplotes telomerase. The data provide a direct demonstration of a template function for a telomerase RNA and demarcate the outer boundaries of the telomeric template.

Author(s): 
Shippen-Lentz, D.
Blackburn, E. H.
Publication Title: 
The EMBO journal

Telomerase, an essential ribonucleoprotein reverse transcriptase, adds telomeric DNA to the ends of eukaryotic chromosomes. We examined the conformational properties of the naked RNA moiety of telomerase from two related ciliates, Tetrahymena thermophila and Glaucoma chattoni. As well as finding evidence for features proposed previously on the basis of phylogenetic comparisons, novel conserved structural properties were revealed.

Author(s): 
Bhattacharyya, A.
Blackburn, E. H.
Publication Title: 
Science (New York, N.Y.)

The ribonucleoprotein enzyme telomerase synthesizes telomeric DNA by copying an internal RNA template sequence. The telomerase activities of the yeasts Saccharomyces castellii and Saccharomyces cerevisiae--with regular and irregular telomeric sequences, respectively--have now been identified and characterized. The S. cerevisiae activity required the telomerase RNA gene TLC1 but not the EST1 gene, both of which are required for normal telomere maintenance in vivo. This activity exhibited low processivity and produced no regularly repeated products.

Author(s): 
Cohn, M.
Blackburn, E. H.
Publication Title: 
The Journal of Eukaryotic Microbiology

Site-directed mutagenesis of the telomerase RNA from Tetrahymena thermophila was used previously to demonstrate the templating function of a sequence within this RNA; this sequence specifies the sequence of telomeric DNA in vivo. The possible functional importance of a phylogenetically conserved nucleotide outside the telomerase RNA template region was investigated by a similar experimental approach.

Author(s): 
Romero, D. P.
Blackburn, E. H.
Publication Title: 
Annual Review of Biochemistry
Author(s): 
Blackburn, E. H.

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