Author
Miriam S. Singer
Bio: Miriam S. Singer is an academic researcher from University of Chicago. The author has contributed to research in topics: RNA & Telomerase. The author has an hindex of 6, co-authored 9 publications receiving 1480 citations.
Topics: RNA, Telomerase, Gene, Telomere, Telomerase RNA component
Papers
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TL;DR: The discovery of TLC1 confirms the existence of telomerase in S. cerevisiae and may facilitate both the analysis of this enzyme and an understanding of telomere structure and function.
Abstract: Telomeres, the natural ends of linear eukaryotic chromosomes, are essential for chromosome stability. Because of the nature of DNA replication, telomeres require a specialized mechanism to ensure their complete duplication. Telomeres are also capable of silencing the transcription of genes that are located near them. In order to identify genes in the budding yeast Saccharomyces cerevisiae that are important for telomere function, a screen was conducted for genes that, when expressed in high amounts, would suppress telomeric silencing. This screen lead to the identification of the gene TLC1 (telomerase component 1). TLC1 encodes the template RNA of telomerase, a ribonucleoprotein required for telomere replication in a variety of organisms. The discovery of TLC1 confirms the existence of telomerase in S. cerevisiae and may facilitate both the analysis of this enzyme and an understanding of telomere structure and function.
770 citations
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TL;DR: A genetic screen to identify genes whose overexpression disrupts telomeric silencing isolated 10 DOT genes, which include both components and regulators of silent chromatin, suggesting that DOT1 and DOT4 normally play important roles in gene repression.
Abstract: The ends of chromosomes in Saccharomyces cerevisiae initiate a repressive chromatin structure that spreads internally and inhibits the transcription of nearby genes, a phenomenon termed telomeric silencing. To investigate the molecular basis of this process, we carried out a genetic screen to identify genes whose overexpression disrupts telomeric silencing. We thus isolated 10 DOT genes (disruptor of telomeric silencing). Among these were genes encoding chromatin component Sir4p, DNA helicase Dna2p, ribosomal protein L32, and two proteins of unknown function, Asf1p and Ifh1p. The collection also included genes that had not previously been identified: DOT1, DOT4, DOT5, DOT6, and TLC1, which encodes the RNA template component of telomerase. With the exception of TLC1, all these genes, particularly DOT1 and DOT4, also reduced silencing at other repressed loci (HM loci and rDNA) when overexpressed. Moreover, deletion of the latter two genes weakened silencing as well, suggesting that DOT1 and DOT4 normally play important roles in gene repression. DOT1 deletion also affected telomere tract length. The function of Dot1p is not known. The sequence of Dot4p suggests that it is a ubiquitin-processing protease. Taken together, the DOT genes include both components and regulators of silent chromatin.
469 citations
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TL;DR: It is shown that a 48-nt stem-loop structure within the 1.3-kb TLC1 RNA is necessary and sufficient for disrupting telomeric silencing and shortening telomeres and this short RNA sequence appears to function through an interaction with the conserved DNA end-binding protein Ku.
Abstract: The telomerase enzyme lengthens telomeres, an activity essential for chromosome stability in most eukaryotes. The enzyme is composed of a specialized reverse transcriptase and a template RNA (ref. 1). In Saccharomyces cerevisiae, overexpression of TLC1, the telomerase RNA gene, disrupts telomeric structure2. The result is both shortened telomere length and loss of a special chromatin structure that normally silences telomere-proximal genes. Because telomerase function is not required for telomeric silencing, we postulated that the dominant-negative effect caused by overexpression of TLC1 RNA originates in a normal interaction between the RNA and an unknown telomeric factor important for silencing; the overexpressed RNA presumably continues to bind the factor and compromises its function3. Here we show that a 48-nt stem-loop structure within the 1.3-kb TLC1 RNA is necessary and sufficient for disrupting telomeric silencing and shortening telomeres. Moreover, this short RNA sequence appears to function through an interaction with the conserved DNA end-binding protein Ku (ref. 4). We propose that, in addition to its roles in telomeric silencing, homologous recombination and non-homologous end-joining (NHEJ), S. cerevisiae Ku also helps to recruit or activate telomerase at the telomere through an interaction with this stem-loop of TLC1 RNA.
232 citations
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01 Aug 1996
TL;DR: In this article, various methods, compositions and screening assays connected with telomerase, including genes encoding the template RNA of S. cerevisiae telomerases and various associated polypeptides, are discussed.
Abstract: Disclosed are various methods, compositions and screening assays connected with telomerase, including genes encoding the template RNA of S. cerevisiae telomerase and various telomerase-associated polypeptides.
17 citations
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30 Jun 1999
TL;DR: In this article, various methods, compositions and screening assays connected with telomerase, including genes encoding the template RNA of S. cerevisiae telomerases and various associated polypeptides, are discussed.
Abstract: Disclosed are various methods, compositions and screening assays connected with telomerase, including genes encoding the template RNA of S. cerevisiae telomerase and various telomerase-associated polypeptides.
15 citations
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TL;DR: Human cell lines that expressed hTR mutated in the template region generated the predicted mutant telomerase activity, and cells transfected with an antisense hTR lost telomeric DNA and began to die after 23 to 26 doublings.
Abstract: Eukaryotic chromosomes are capped with repetitive telomere sequences that protect the ends from damage and rearrangements. Telomere repeats are synthesized by telomerase, a ribonucleic acid (RNA)-protein complex. Here, the cloning of the RNA component of human telomerase, termed hTR, is described. The template region of hTR encompasses 11 nucleotides (5'-CUAACCCUAAC) complementary to the human telomere sequence (TTAGGG)n. Germline tissues and tumor cell lines expressed more hTR than normal somatic cells and tissues, which have no detectable telomerase activity. Human cell lines that expressed hTR mutated in the template region generated the predicted mutant telomerase activity. HeLa cells transfected with an antisense hTR lost telomeric DNA and began to die after 23 to 26 doublings. Thus, human telomerase is a critical enzyme for the long-term proliferation of immortal tumor cells.
2,305 citations
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TL;DR: This review encompasses different aspects of DSB-induced recombination in Saccharomyces and attempts to relate genetic, molecular biological, and biochemical studies of the processes of DNA repair and recombination.
Abstract: The budding yeast Saccharomyces cerevisiae has been the principal organism used in experiments to examine genetic recombination in eukaryotes. Studies over the past decade have shown that meiotic recombination and probably most mitotic recombination arise from the repair of double-strand breaks (DSBs). There are multiple pathways by which such DSBs can be repaired, including several homologous recombination pathways and still other nonhomologous mechanisms. Our understanding has also been greatly enriched by the characterization of many proteins involved in recombination and by insights that link aspects of DNA repair to chromosome replication. New molecular models of DSB-induced gene conversion are presented. This review encompasses these different aspects of DSB-induced recombination in Saccharomyces and attempts to relate genetic, molecular biological, and biochemical studies of the processes of DNA repair and recombination.
2,175 citations
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TL;DR: Results indicate that telomerase is essential for telomere length maintenance but is not required for establishment of cell lines, oncogenic transformation, or tumor formation in mice.
2,066 citations
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TL;DR: The structure of telomeres, the protective DNA-protein complexes at eukaryotic chromosomal ends, and several molecular mechanisms involved in telomere functions are described.
2,000 citations
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TL;DR: The cloning of a human gene, hEST2, that shares significant sequence similarity with the telomerase catalytic subunit genes of lower eukaryotes is reported, suggesting that the induction of hEST 2 mRNA expression is required for the telomersase activation that occurs during cellular immortalization and tumor progression.
1,907 citations