Repetitive Sequences, Nucleic Acid

Publication Title: 
Scientific American
Author(s): 
Sinclair, David A.
Guarente, Lenny
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: 
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: 
Cell

The germ-line micronuclear genome of the ciliate Tetrahymena thermophila contains approximately 10(2) chromosome-internal blocks of tandemly repeated C4A2 sequences (mic C4A2). This repeated sequence is the telomeric sequence in the somatic macronucleus. Each of six cloned micC4A2 was found to be adjacent to a conserved 30 bp sequence, which we propose is the terminal inverted repeat of a family of DNA elements (the Tel-1 family).

Author(s): 
Cherry, J. M.
Blackburn, E. H.
Publication Title: 
Molecular and Cellular Biology

The ribonucleoprotein telomerase, a specialized cellular reverse transcriptase, synthesizes one strand of the telomeric DNA of eukaryotes. We analyzed telomere maintenance in two immortalized human cell lines: the B-cell line JY616 and the T-cell line Jurkat E6-1, and determined whether known inhibitors of retroviral reverse transcriptases could perturb telomere lengths and growth rates of these cells in culture. Dideoxyguanosine (ddG) caused reproducible, progressive telomere shortening over several weeks of passaging, after which the telomeres stabilized and remained short.

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: 
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: 
Proceedings of the National Academy of Sciences of the United States of America

A tandemly repeated DNA hexanucleotide sequence, 5'C-C-C-C-A-A3', that occurs at the termini of extrachromosomal DNA molecules coding for rRNA (rDNA) in Tetrahymena macronuclei was examined to determine whether it is packaged as nucleosomes. This repeated DNA sequence comprises the terminal few hundred base pairs at each end of the linear rDNA molecules.

Author(s): 
Blackburn, E. H.
Chiou, S. S.
Publication Title: 
The Journal of Cell Biology

The ribosomal RNA genes of the Tetrahymena macronucleus exist as extrachromosomal, linear molecules. The termini of these molecules have been shown to contain the tandemly repeated hexanucleotide (C-C-C-C-A-A)n. In this study the same or related sequences were found in other locations of the genome. Using the depurination method, we showed that macronuclear DNA contained this sequence even after rDNA had been removed. The sequence was found mainly in the repetitive fraction of the DNA.

Author(s): 
Yao, M. C.
Blackburn, E.
Gall, J.

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