Intracellular trafficking of yeast telomerase components

Swiss Institute for Experimental Cancer Research (ISREC), Epalinges, Switzerland.
EMBO Reports (Impact Factor: 9.06). 08/2002; 3(7):652-9. DOI: 10.1093/embo-reports/kvf133
Source: PubMed


Telomerase uses an internal RNA moiety as template for the synthesis of telomere repeats. In Saccharomyces cerevisiae, the telomerase holoenzyme contains the telomerase reverse transcriptase subunit Est2p, the telomerase RNA moiety TLC1, the telomerase associated proteins Est1p and Est3p, and Sm proteins. Here we assess telomerase assembly by determining the localization of telomerase components. We found that Est1p, Est2p and TLC1 can migrate independently of each other to the nucleus. With limiting amounts of TLC1, overexpressed Est1p and Est2p accumulated in the nucleolus, whereas enzymatically active Est2p-TLC1 complexes are distributed over the entire nucleus. The distribution to the nucleoplasm depended on the specific interaction between Est2p and TLC1 but was independent of Est1p and Est3p. Altogether, our results suggest a role of the nucleolus in telomerase biogenesis. We also describe experiments that support a transient cytoplasmic localization of TLC1 RNA.

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Available from: Susan M Gasser
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    • "It has been well documented that the telomerase travels to the cytoplasm, however the biological significance of the cytoplasmic phase on the regulation of telomerase RNA remains unclear [32], [33], [34]. In metazoans, snRNA maturation requires export to the cytoplasm, where the cap structure undergoes hypermethylation. "
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    ABSTRACT: A key question in the field of RNA regulation is how some exosome substrates, such as spliceosomal snRNAs and telomerase RNA, evade degradation and are processed into stable, functional RNA molecules. Typical feature of these non-coding RNAs is presence of the Sm complex at the 3'end of the mature RNA molecule. Here, we report that in Saccharomyces cerevisiae presence of intact Sm binding site is required for the exosome-mediated processing of telomerase RNA from a polyadenylated precursor into its mature form and is essential for its function in elongating telomeres. Additionally, we demonstrate that the same pathway is involved in the maturation of snRNAs. Furthermore, the insertion of an Sm binding site into an unstable RNA that is normally completely destroyed by the exosome, leads to its partial stabilization. We also show that telomerase RNA accumulates in Schizosaccharomyces pombe exosome mutants, suggesting a conserved role for the exosome in processing and degradation of telomerase RNA. In summary, our data provide important mechanistic insight into the regulation of exosome dependent RNA processing as well as telomerase RNA biogenesis.
    Full-text · Article · Jun 2013 · PLoS ONE
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    • "The nucleolus seems to be coupled with variety of telomeric functions, given that many telomere-related functions are known to localize in the nucleoli in Arabidopsis and other organisms. For example, telomerase localizes in the nucleoli during S phase in mammalian cells and yeast (Etheridge et al., 2002; Teixeira et al., 2002; Wong et al., 2002; Khurts et al., 2004; Yan et al., 2004) and the N-terminal part of AtTERT is localized in the nucleolus in Arabidopsis (Rossignol et al., 2007). The telomere-associated protein, Rap1, from yeast is a Myb-like protein with additional functions in transcription (Horvath, 2008). "
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    ABSTRACT: AtTRB1, 2 and 3 are members of the SMH (single Myb histone) protein family, which comprises double-stranded DNA-binding proteins that are specific to higher plants. They are structurally conserved, containing a Myb domain at the N-terminus, a central H1/H5-like domain and a C-terminally located coiled-coil domain. AtTRB1, 2 and 3 interact through their Myb domain specifically with telomeric double-stranded DNA in vitro, while the central H1/H5-like domain interacts non-specifically with DNA sequences and mediates protein-protein interactions. Here we show that AtTRB1, 2 and 3 preferentially localize to the nucleus and nucleolus during interphase. Both the central H1/H5-like domain and the Myb domain from AtTRB1 can direct a GFP fusion protein to the nucleus and nucleolus. AtTRB1-GFP localization is cell cycle-regulated, as the level of nuclear-associated GFP diminishes during mitotic entry and GFP progressively re-associates with chromatin during anaphase/telophase. Using fluorescence recovery after photobleaching and fluorescence loss in photobleaching, we determined the dynamics of AtTRB1 interactions in vivo. The results reveal that AtTRB1 interaction with chromatin is regulated at two levels at least, one of which is coupled with cell-cycle progression, with the other involving rapid exchange.
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    • "Telomerases differ in catalytic properties such as processivity and fidelity, and telomerases of some organisms function as dimers (Beattie et al., 2001; Wenz et al., 2001; reviewed in Ly et al., 2003; Autexier and Lue, 2006; Cohen et al., 2007). Biosynthesis of both subunits, TERT and TR, is not directly connected, and differential regulation raises questions of intracellular/intranuclear trafficking and their assembly to form an active telomerase (Teixeira et al., 2002; Tomlinson et al., 2006; for reviews see Collins, 2006; Hug and Lingner, 2006; Cairney and Keith, 2008; Gallardo et al., 2008). Generally, functional telomerase in vivo has many inter-related activities (Figure 1), including RNA–protein interactions (binding of TR and TERT subunits), DNA–protein interactions (binding to substrate), RT activity and protein–protein interactions (e.g. "
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    ABSTRACT: The TERT (telomerase reverse transcriptase) subunit of telomerase is an intensively studied macromolecule due to its key importance in maintaining genome integrity and role in cellular aging and cancer. In an effort to provide an up-to-date overview of the topic, we discuss the structure of TERT genes, their alternative splicing products and their functions. Nucleotide databases contain more than 90 full-length cDNA sequences of telomerase protein subunits. Numerous in silico, in vitro and in vivo experimental techniques have revealed a great deal of structural and functional data describing particular features of the telomerase subunit in various model organisms. We explore whether particular findings are generally applicable to telomerases or species-specific. We also discuss in an evolutionary context the role of identified functional TERT subdomains.
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