Telomerase structure function

Mason, Mark; Schuller, Anthony P.; Skordalakes, Emmanuel

doi:10.1016/j.sbi.2010.11.005

Cited by 66 publications

(57 citation statements)

References 58 publications

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“…Intriguingly, the catalytic domain of telomerase reverse transcriptase (TERT) has structural and functional characteristics in common with picornaviral RNA-dependent RNA polymerases. The catalytic domain of TERT assumes a right-hand conformation, with thumb, palm, and fingers domains encircling the telomerase RNA template and cDNA products (53)(54)(55). Furthermore, TERT uses a template-dependent reiterative transcription mechanism to synthesize repetitive DNA sequences of variable length at the 3= end of eukaryotic chromosomes (56).…”

Section: Discussionmentioning

confidence: 99%

Structural Features of a Picornavirus Polymerase Involved in the Polyadenylation of Viral RNA

Kempf

Kelly²,

Springer

et al. 2013

J Virol

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Picornaviruses have 3= polyadenylated RNA genomes, but the mechanisms by which these genomes are polyadenylated during viral replication remain obscure. Based on prior studies, we proposed a model wherein the poliovirus RNA-dependent RNA polymerase (3D pol ) uses a reiterative transcription mechanism while replicating the poly(A) and poly(U) portions of viral RNA templates. To further test this model, we examined whether mutations in 3D pol influenced the polyadenylation of virion RNA. We identified nine alanine substitution mutations in 3D pol that resulted in shorter or longer 3= poly(A) tails in virion RNA. These mutations could disrupt structural features of 3D pol required for the recruitment of a cellular poly(A) polymerase; however, the structural orientation of these residues suggests a direct role of 3D pol in the polyadenylation of RNA genomes. Reaction mixtures containing purified 3D pol and a template RNA with a defined poly(U) sequence provided data consistent with a template-dependent reiterative transcription mechanism for polyadenylation. The phylogenetically conserved structural features of 3D pol involved in the polyadenylation of virion RNA include a thumb domain alpha helix that is positioned in the minor groove of the double-stranded RNA product and lysine and arginine residues that interact with the phosphates of both the RNA template and product strands.P icornaviruses, like many other positive-strand RNA viruses, have RNA genomes with variable-length 3= poly(A) tails (1). The poly(A) tails of picornaviruses are important for viability (2), with the length of the poly(A) tails influencing the magnitudes of both viral mRNA translation and RNA replication (3, 4). RNA sequences and structures within the 3= nontranslated region are reported to influence both the length of poly(A) tails in picornaviral RNA (5) and the efficiency of virus replication (6, 7). Viral RNA-dependent RNA polymerases (3D pol s) are predicted to catalyze the polyadenylation of picornaviral RNA in a template-dependent manner during viral RNA replication (8); however, the mechanisms by which RNA genomes are polyadenylated during viral RNA replication remain obscure. In particular, there is little understanding of the mechanisms regulating the length of poly(A) tails synthesized during RNA replication. The RNA-dependent RNA polymerases of negative-strand RNA viruses reiteratively transcribe a small poly(U) sequence within intergenic regions of the viral RNA genome to produce long poly(A) tails on viral mRNAs (9). In a similar manner, the poliovirus RNA-dependent RNA polymerase can reiteratively transcribe poly(A) and poly(U) sequences during viral RNA replication, producing poly(A) and poly(U) sequences longer than those in the respective template RNAs (8).Viral RNA-dependent RNA polymerases are well studied at the structural level (10-12), yet there have been no reports describing the structural features of viral polymerases involved in the polyadenylation of viral RNA. The RNA-dependent RNA polymerase of picornaviruses a...

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Section: Discussionmentioning

confidence: 99%

Structural Features of a Picornavirus Polymerase Involved in the Polyadenylation of Viral RNA

Kempf

Kelly²,

Springer

et al. 2013

J Virol

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“…It is noteworthy that the biochemical characteristics of yeast, ciliate, and human telomerases are quite different. For example, they show differences in processivity and associate with different complements of proteins, and their RNA templates differ vastly (Mason et al 2011). Thus, it is quite remarkable that the importance of dGTP levels on telomerase activity is highly conserved, even if the precise mechanism may differ in different species.…”

Section: Mec1 Mediates Telomere Length Homeostasis By Regulating Dntpmentioning

confidence: 99%

Telomere Length Homeostasis Responds to Changes in Intracellular dNTP Pools

et al. 2013

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Telomeres, the ends of linear eukaryotic chromosomes, shorten due to incomplete DNA replication and nucleolytic degradation. Cells counteract this shortening by employing a specialized reverse transcriptase called telomerase, which uses deoxyribonucleoside triphosphates (dNTPs) to extend telomeres. Intracellular dNTP levels are tightly regulated, and perturbation of these levels is known to affect DNA synthesis. We examined whether altering the levels of the dNTP pools or changing the relative ratios of the four dNTPs in Saccharomyces cerevisiae would affect the length of the telomeres. Lowering dNTP levels leads to a modest shortening of telomeres, while increasing dNTP pools has no significant effect on telomere length. Strikingly, altering the ratio of the four dNTPs dramatically affects telomere length homeostasis, both positively and negatively. Specifically, we find that intracellular deoxyguanosine triphosphate (dGTP) levels positively correlate with both telomere length and telomerase nucleotide addition processivity in vivo. Our findings are consistent with in vitro data showing dGTP-dependent stimulation of telomerase activity in multiple organisms and suggest that telomerase activity is modulated in vivo by dGTP levels.A LL eukaryotes, as well as some prokaryotes with linear chromosomes, contain repetitive sequences called telomeres at the ends of their DNA. Telomeric DNA is bound by proteins that protect chromosome ends from being recognized as genotoxic DNA double-strand breaks in need of repair (Jain and Cooper 2010). However, telomeres shorten due to incomplete DNA replication and nucleolytic degradation. Left unchecked, this telomere erosion eventually results in very short, unprotected telomeres, leading to cell-cycle arrest and replicative senescence (Lundblad and Szostak 1989;Harley et al. 1990;Yu et al. 1990).Telomere shortening is counteracted by a specialized reverse transcriptase called telomerase (Greider and Blackburn 1985), whose core consists of a protein catalytic subunit and an RNA moiety-hTERT and hTR, respectively, in humans (Feng et al. 1995;Nakamura et al. 1997), and Est2 and TLC1, respectively, in the budding yeast Saccharomyces cerevisiae (Singer and Gottschling 1994;Lingner et al. 1997). Telomerase extends telomeres by repeated reverse transcription of a short sequence to the 39 ends of telomeres, using the RNA subunit as a template (Greider and Blackburn 1989;Yu et al. 1990;Singer and Gottschling 1994). Although the sequence of the telomeric repeats differs between species, a common feature is that they are all G-rich. In vertebrates, the repeat sequence is TTAGGG (Meyne et al. 1989), while in S. cerevisiae, the telomeric repeats have a consensus sequence of (TG) 0-6 TGGGTGTG(G) 0-1 (Forstemann and Lingner 2001).Deoxyribonucleoside triphosphates (dNTPs) are the building blocks of DNA, and their production needs to be tightly regulated as imbalances in dNTP pools can be mutagenic (Reichard 1988). In S. cerevisiae, the sole mode of dNTP production is through de novo dN...

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“…But cancer cells could escape this limitation. Telomeres would be completely repaired by telomerase and related proteins in cancer cells contributes to the phenomenon (Hanahan et al, 2011;Mason et al, 2011), which are mediated by a stably associated complex-shelterin. Shelterin which is composed of six telomere proteins, including TRF1 (telomere repeat binding factor 1), TRF2 (telomere repeat binding factor 2), TIN2 (TRF1-interacting factor 2), TPP1 (POT1 and TIN2-interacting protein), Rap1 (telomeric repeat-binding factor 2-interacting protein 1) and POT1 (protection of telomeres) (de Lange, 2005;Diotti et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

Expression of hPOT1 in HeLa Cells and the Probability of Gene Variation of hpot1 Exon14 in Endometrial Cancer are Much Higher than in Other Cancers

Liu

Pu²,

Huang³

et al. 2012

Asian Pacific Journal of Cancer Prevention

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To investigate the expression of hPOT1 in the HeLa cell line and screen point mutations of hpot1 in different tumor tissues a two step osmotic method was used to extract nuclear proteins. EMSA was performed to determine the expression of hPOT1 in the HeLa cell line. PCR was also employed to amplify the exon14 sequence of the hpot1 gene in various of cancer tissues. A SV gel and PCR clean-up system was performed to enrich PCR products. DNAStar was used to analyse the exon14 sequence of the hpot1 gene. hPOT1 was expressed in the HeLa cell line and the signal was gradually enhanced as the amount of extracted nuclear proteins increased. The DNA fragment of exon14 of hpot1 was successfully amplified in the HeLa cell line and all cancer tissues, point mutations being observed in 2 out of 3 cases of endometrial cancer (66.7%) despite the hpot1 sequence being highly conserved. However, the sequence of hpot1 exon14 do not demonstrate point mutations in most cancer tissues. Since hPOT1 was expressed in HeLa cell and the probability of gene point variants was obviously higher in endometrial cancer than other cancers, it may be involved in the pathogenesis of gynecological cancers, especially in cervix and endometrium.

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Telomerase structure function

Cited by 66 publications

References 58 publications

Structural Features of a Picornavirus Polymerase Involved in the Polyadenylation of Viral RNA

Structural Features of a Picornavirus Polymerase Involved in the Polyadenylation of Viral RNA

Telomere Length Homeostasis Responds to Changes in Intracellular dNTP Pools

Expression of hPOT1 in HeLa Cells and the Probability of Gene Variation of hpot1 Exon14 in Endometrial Cancer are Much Higher than in Other Cancers

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