A popular engagement at the ends

Lue, Neal F.; Yu, Eun Young; Lei, Ming

doi:10.1038/nsmb.2483

Cited by 8 publications

(9 citation statements)

References 28 publications

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“…For simplification, the N-term tail has been removed from this view; the structure starts at R96 instead of S90 in the PDB 2I46 structure. (36) is the same as a recently reported model of Est3 (32). As a result of these differences, functionally important residues (same as A) map to scattered locations on the predicted model's surface unlike Fig.…”

Section: Discussionsupporting

confidence: 58%

Structure of Est3 reveals a bimodal surface with differential roles in telomere replication

Rao

Lubin

Armstrong

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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Telomerase is essential for continuous cellular proliferation. Substantial insights have come from studies of budding yeast telomerase, which consists of a catalytic core in association with two regulatory proteins, ever shorter telomeres 1 and 3 (Est1 and Est3). We report here a high-resolution structure of the Est3 telomerase subunit determined using a recently developed strategy that combines minimal NMR experimental data with Rosetta de novo structure prediction algorithms. Est3 adopts an overall protein fold which is structurally similar to that adopted by the shelterin component TPP1. However, the characteristics of the surface of the experimentally determined Est3 structure are substantially different from those predicted by prior homology-based models of Est3. Structure-guided mutagenesis of the complete surface of the Est3 protein reveals two adjacent patches on a noncanonical face of the protein that differentially mediate telomere function. Mapping these two patches on the Est3 structure defines a set of shared features between Est3 and HsTPP1, suggesting an analogous multifunctional surface on TPP1.RASREC Rosetta | OB-fold protein T elomerase is a telomere-dedicated DNA polymerase that is responsible for telomere-length maintenance in most eukaryotes. In cells that lack telomerase, gradual erosion due to incomplete replication of duplex telomeric DNA leads to an eventual block to cellular proliferation. Ectopic expression of telomerase in human cells is sufficient to confer cellular immortality (1) and it is up-regulated in over 90% of tumor biopsies (2). Conversely, reduced telomerase activity is responsible for the age-dependent effects on organs that rely on continual replenishment throughout a normal human life span and can lead to bone marrow failure, pulmonary fibrosis, or aplastic anemia (3). Hence, an increased understanding of the roles of telomerase and its accessory proteins in telomere length homeostasis has the potential to impact several different aspects of human health.The yeast telomerase holoenzyme is composed of three proteins [the catalytic ever shorter telomere 2 (Est2) subunit, along with the Est1 and Est3 regulatory proteins], which together form a complex with the TLC1 RNA (4, 5). In vivo, telomerase is highly regulated, in that only a subset of telomeres are elongated in each cell cycle (6); however, the mechanism that restricts telomerase to a limited number of substrates is still poorly understood. This deficit stems at least in part from the fact that the surface of yeast telomerase represents a largely unexplored territory. Even though there are numerous interaction surfaces on the three Est proteins with the potential to regulate important interactions, the only well-characterized regulatory step involving Est proteins is the recruitment of telomerase to the telomere through the direct interaction of Est1 and the end-binding protein Cdc13 (7), which was originally uncovered using a labor-intensive genetic approach (8).High-resolution structural information provides a str...

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Section: Discussionsupporting

confidence: 58%

Structure of Est3 reveals a bimodal surface with differential roles in telomere replication

Rao

Lubin

Armstrong

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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“…hTERT regulates telomere length homeostasis by shortening long telomeres and elongating short telomeres, and these 2 opposing but biologically interactive functions appear to be regulated by local factors, such as telomere length at a specific chromosomal end, and are likely to involve telomere length counting as illustrated in budding yeast, in which Rif1 and Rif2 were proposed molecules to be counted for length determination, and Rap1, a telomere binding protein, recruits Rif proteins to the telomeric track. 30,31 The mechanism underlying the telomere length counting in human cells is largely unknown. Our data indicated that TPP1, a member of shelterin protein complex, is required in the hTERT-mediated telomere-shortening process.…”

Section: Discussionmentioning

confidence: 99%

Telomerase enzymatic component hTERT shortens long telomeres in human cells

et al. 2014

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“…Three functions for TPP1 in telomerase action at telomeres Previous studies of cellular phenotypes due to TPP1 depletion demonstrated roles of TPP1 in shelterin-mediated protection of telomere integrity, negative regulation of telomerase through POT1, and telomerase physical and functional recruitment to telomeric chromatin (Palm and de Lange 2008;Lue et al 2013;Nandakumar and Cech 2013). The resolution of distinct TPP1 roles in shelterin assembly and telomerase action was greatly aided by discovery of the TEL patch dependence of TPP1 association to active telomerase (Nandakumar et al 2012;Sexton et al 2012;Zhong et al 2012).…”

Section: Tpp1 Function In Telomere Length Control Genes and Developmentmentioning

confidence: 99%

“…Depletion and overexpression experiments establish TPP1 and POT1 as negative regulators of telomere length (Loayza and de Lange 2003;Houghtaling et al 2004;Liu et al 2004;Ye et al 2004;Hockemeyer et al 2007;Churikov and Price 2008;Baumann and Price 2010). Recent studies using protein expression knockdown suggest that TPP1 also promotes telomerase activity at telomeres (Lue et al 2013;Nakashima et al 2013). The TPP1 oligonucleotide/oligosaccharide-binding fold (OB) and specifically an OB surface termed the TEL patch mediate the interaction of TPP1 and telomerase assayed by coimmunopurification of overexpressed proteins from cell extract, cellular colocalization of overexpressed proteins, and extent of telomere elongation in human tumor cell lines (Wang et al 2007;Xin et al 2007;Abreu et al 2010;Tejera et al 2010;Nandakumar et al 2012;Sexton et al 2012;Zhong et al 2012).…”

mentioning

confidence: 99%

Genetic and molecular identification of three human TPP1 functions in telomerase action: recruitment, activation, and homeostasis set point regulation

et al. 2014

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Telomere length homeostasis is essential for the long-term survival of stem cells, and its set point determines the proliferative capacity of differentiated cell lineages by restricting the reservoir of telomeric repeats. Knockdown and overexpression studies in human tumor cells showed that the shelterin subunit TPP1 recruits telomerase to telomeres through a region termed the TEL patch. However, these studies do not resolve whether the TPP1 TEL patch is the only mechanism for telomerase recruitment and whether telomerase regulation studied in tumor cells is representative of nontransformed cells such as stem cells. Using genome engineering of human embryonic stem cells, which have physiological telomere length homeostasis, we establish that the TPP1 TEL patch is genetically essential for telomere elongation and thus long-term cell viability. Furthermore, genetic bypass, protein fusion, and intragenic complementation assays define two distinct additional mechanisms of TPP1 involvement in telomerase action at telomeres. We demonstrate that TPP1 provides an essential step of telomerase activation as well as feedback regulation of telomerase by telomere length, which is necessary to determine the appropriate telomere length set point in human embryonic stem cells. These studies reveal and resolve multiple TPP1 roles in telomere elongation and stem cell telomere length homeostasis.

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A popular engagement at the ends

Cited by 8 publications

References 28 publications

Structure of Est3 reveals a bimodal surface with differential roles in telomere replication

Structure of Est3 reveals a bimodal surface with differential roles in telomere replication

Telomerase enzymatic component hTERT shortens long telomeres in human cells

Genetic and molecular identification of three human TPP1 functions in telomerase action: recruitment, activation, and homeostasis set point regulation

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