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Imran SAM, Yazid MD, Idrus RBH, Maarof M, Nordin A, Razali RA, Lokanathan Y. Is There an Interconnection between Epithelial-Mesenchymal Transition (EMT) and Telomere Shortening in Aging? Int J Mol Sci 2021; 22:ijms22083888. [PMID: 33918710 PMCID: PMC8070110 DOI: 10.3390/ijms22083888] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2021] [Revised: 04/07/2021] [Accepted: 04/07/2021] [Indexed: 12/12/2022] Open
Abstract
Epithelial–Mesenchymal Transition (EMT) was first discovered during the transition of cells from the primitive streak during embryogenesis in chicks. It was later discovered that EMT holds greater potential in areas other than the early development of cells and tissues since it also plays a vital role in wound healing and cancer development. EMT can be classified into three types based on physiological functions. EMT type 3, which involves neoplastic development and metastasis, has been the most thoroughly explored. As EMT is often found in cancer stem cells, most research has focused on its association with other factors involving cancer progression, including telomeres. However, as telomeres are also mainly involved in aging, any possible interaction between the two would be worth noting, especially as telomere dysfunction also contributes to cancer and other age-related diseases. Ascertaining the balance between degeneration and cancer development is crucial in cell biology, in which telomeres function as a key regulator between the two extremes. The essential roles that EMT and telomere protection have in aging reveal a potential mutual interaction that has not yet been explored, and which could be used in disease therapy. In this review, the known functions of EMT and telomeres in aging are discussed and their potential interaction in age-related diseases is highlighted.
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Affiliation(s)
- Siti A. M. Imran
- Centre for Tissue Engineering and Regenerative Medicine, Faculty of Medicine, Universiti Kebangsaan Malaysia, Jalan Yaacob Latiff, Bandar Tun Razak, Cheras, Kuala Lumpur 56000, Malaysia; (S.A.M.I.); (M.D.Y.); (R.B.H.I.); (M.M.); (A.N.); (R.A.R.)
| | - Muhammad Dain Yazid
- Centre for Tissue Engineering and Regenerative Medicine, Faculty of Medicine, Universiti Kebangsaan Malaysia, Jalan Yaacob Latiff, Bandar Tun Razak, Cheras, Kuala Lumpur 56000, Malaysia; (S.A.M.I.); (M.D.Y.); (R.B.H.I.); (M.M.); (A.N.); (R.A.R.)
| | - Ruszymah Bt Hj Idrus
- Centre for Tissue Engineering and Regenerative Medicine, Faculty of Medicine, Universiti Kebangsaan Malaysia, Jalan Yaacob Latiff, Bandar Tun Razak, Cheras, Kuala Lumpur 56000, Malaysia; (S.A.M.I.); (M.D.Y.); (R.B.H.I.); (M.M.); (A.N.); (R.A.R.)
- Department of Physiology, Faculty of Medicine, Universiti Kebangsaan Malaysia, Jalan Yaacob Latiff, Bandar Tun Razak, Cheras, Kuala Lumpur 56000, Malaysia
| | - Manira Maarof
- Centre for Tissue Engineering and Regenerative Medicine, Faculty of Medicine, Universiti Kebangsaan Malaysia, Jalan Yaacob Latiff, Bandar Tun Razak, Cheras, Kuala Lumpur 56000, Malaysia; (S.A.M.I.); (M.D.Y.); (R.B.H.I.); (M.M.); (A.N.); (R.A.R.)
| | - Abid Nordin
- Centre for Tissue Engineering and Regenerative Medicine, Faculty of Medicine, Universiti Kebangsaan Malaysia, Jalan Yaacob Latiff, Bandar Tun Razak, Cheras, Kuala Lumpur 56000, Malaysia; (S.A.M.I.); (M.D.Y.); (R.B.H.I.); (M.M.); (A.N.); (R.A.R.)
- Department of Physiology, Faculty of Medicine, Universiti Kebangsaan Malaysia, Jalan Yaacob Latiff, Bandar Tun Razak, Cheras, Kuala Lumpur 56000, Malaysia
| | - Rabiatul Adawiyah Razali
- Centre for Tissue Engineering and Regenerative Medicine, Faculty of Medicine, Universiti Kebangsaan Malaysia, Jalan Yaacob Latiff, Bandar Tun Razak, Cheras, Kuala Lumpur 56000, Malaysia; (S.A.M.I.); (M.D.Y.); (R.B.H.I.); (M.M.); (A.N.); (R.A.R.)
- Department of Physiology, Faculty of Medicine, Universiti Kebangsaan Malaysia, Jalan Yaacob Latiff, Bandar Tun Razak, Cheras, Kuala Lumpur 56000, Malaysia
| | - Yogeswaran Lokanathan
- Centre for Tissue Engineering and Regenerative Medicine, Faculty of Medicine, Universiti Kebangsaan Malaysia, Jalan Yaacob Latiff, Bandar Tun Razak, Cheras, Kuala Lumpur 56000, Malaysia; (S.A.M.I.); (M.D.Y.); (R.B.H.I.); (M.M.); (A.N.); (R.A.R.)
- Correspondence: ; Tel.: +60-391457704
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Wu ZJ, Liu JC, Man X, Gu X, Li TY, Cai C, He MH, Shao Y, Lu N, Xue X, Qin Z, Zhou JQ. Cdc13 is predominant over Stn1 and Ten1 in preventing chromosome end fusions. eLife 2020; 9:53144. [PMID: 32755541 PMCID: PMC7406354 DOI: 10.7554/elife.53144] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Accepted: 06/12/2020] [Indexed: 12/16/2022] Open
Abstract
Telomeres define the natural ends of eukaryotic chromosomes and are crucial for chromosomal stability. The budding yeast Cdc13, Stn1 and Ten1 proteins form a heterotrimeric complex, and the inactivation of any of its subunits leads to a uniformly lethal phenotype due to telomere deprotection. Although Cdc13, Stn1 and Ten1 seem to belong to an epistasis group, it remains unclear whether they function differently in telomere protection. Here, we employed the single-linear-chromosome yeast SY14, and surprisingly found that the deletion of CDC13 leads to telomere erosion and intrachromosome end-to-end fusion, which depends on Rad52 but not Yku. Interestingly, the emergence frequency of survivors in the SY14 cdc13Δ mutant was ~29 fold higher than that in either the stn1Δ or ten1Δ mutant, demonstrating a predominant role of Cdc13 in inhibiting telomere fusion. Chromosomal fusion readily occurred in the telomerase-null SY14 strain, further verifying the default role of intact telomeres in inhibiting chromosome fusion.
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Affiliation(s)
- Zhi-Jing Wu
- The State Key Laboratory of Molecular Biology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences; University of Chinese Academy of Sciences, Shanghai, China
| | - Jia-Cheng Liu
- The State Key Laboratory of Molecular Biology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences; University of Chinese Academy of Sciences, Shanghai, China
| | - Xin Man
- The State Key Laboratory of Molecular Biology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences; University of Chinese Academy of Sciences, Shanghai, China
| | - Xin Gu
- The State Key Laboratory of Molecular Biology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences; University of Chinese Academy of Sciences, Shanghai, China
| | - Ting-Yi Li
- The State Key Laboratory of Molecular Biology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences; University of Chinese Academy of Sciences, Shanghai, China
| | - Chen Cai
- The State Key Laboratory of Molecular Biology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences; University of Chinese Academy of Sciences, Shanghai, China.,School of Life Science and Technology, ShanghaiTech University, Shanghai, China
| | - Ming-Hong He
- The State Key Laboratory of Molecular Biology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences; University of Chinese Academy of Sciences, Shanghai, China
| | - Yangyang Shao
- Key Laboratory of Synthetic Biology, CAS Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences; University of Chinese Academy of Sciences, Shanghai, China
| | - Ning Lu
- Key Laboratory of Synthetic Biology, CAS Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences; University of Chinese Academy of Sciences, Shanghai, China
| | - Xiaoli Xue
- Key Laboratory of Synthetic Biology, CAS Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences; University of Chinese Academy of Sciences, Shanghai, China
| | - Zhongjun Qin
- Key Laboratory of Synthetic Biology, CAS Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences; University of Chinese Academy of Sciences, Shanghai, China
| | - Jin-Qiu Zhou
- The State Key Laboratory of Molecular Biology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences; University of Chinese Academy of Sciences, Shanghai, China.,School of Life Science and Technology, ShanghaiTech University, Shanghai, China
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Nugent C, Sugimoto K. Getting to grips with circular chromosomes. eLife 2020; 9:e60150. [PMID: 32755540 PMCID: PMC7406349 DOI: 10.7554/elife.60150] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2020] [Accepted: 07/29/2020] [Indexed: 11/15/2022] Open
Abstract
A strain of budding yeast that contains one large chromosome reveals how the telomere capping complex CST maintains linear but not circular chromosomes.
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Affiliation(s)
- Constance Nugent
- Department of Molecular, Cellular and Systems Biology, University of California, RiversideRiversideUnited States
| | - Katsunori Sugimoto
- Department of Microbiology, Biochemistry and Molecular Genetics, Rutgers New Jersey Medical SchoolNewarkUnited States
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Van Ly D, Low RRJ, Frölich S, Bartolec TK, Kafer GR, Pickett HA, Gaus K, Cesare AJ. Telomere Loop Dynamics in Chromosome End Protection. Mol Cell 2018; 71:510-525.e6. [PMID: 30033372 DOI: 10.1016/j.molcel.2018.06.025] [Citation(s) in RCA: 73] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2018] [Revised: 05/28/2018] [Accepted: 06/15/2018] [Indexed: 01/07/2023]
Abstract
Telomeres regulate DNA damage response (DDR) and DNA repair activity at chromosome ends. How telomere macromolecular structure contributes to ATM regulation and its potential dissociation from control over non-homologous end joining (NHEJ)-dependent telomere fusion is of central importance to telomere-dependent cell aging and tumor suppression. Using super-resolution microscopy, we identify that ATM activation at mammalian telomeres with reduced TRF2 or at human telomeres during mitotic arrest occurs specifically with a structural change from telomere loops (t-loops) to linearized telomeres. Additionally, we find the TRFH domain of TRF2 regulates t-loop formation while suppressing ATM activity. Notably, we demonstrate that ATM activation and telomere linearity occur separately from telomere fusion via NHEJ and that linear DDR-positive telomeres can remain resistant to fusion, even during an extended G1 arrest, when NHEJ is most active. Collectively, these results suggest t-loops act as conformational switches that specifically regulate ATM activation independent of telomere mechanisms to inhibit NHEJ.
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Affiliation(s)
- David Van Ly
- Genome Integrity Unit, Children's Medical Research Institute, University of Sydney, Westmead, NSW 2145, Australia; School of Medicine, The University of Notre Dame Australia, Sydney, NSW 2010, Australia
| | - Ronnie Ren Jie Low
- Genome Integrity Unit, Children's Medical Research Institute, University of Sydney, Westmead, NSW 2145, Australia
| | - Sonja Frölich
- Genome Integrity Unit, Children's Medical Research Institute, University of Sydney, Westmead, NSW 2145, Australia
| | - Tara K Bartolec
- Genome Integrity Unit, Children's Medical Research Institute, University of Sydney, Westmead, NSW 2145, Australia
| | - Georgia R Kafer
- Genome Integrity Unit, Children's Medical Research Institute, University of Sydney, Westmead, NSW 2145, Australia
| | - Hilda A Pickett
- Telomere Length Regulation Unit, Children's Medical Research Institute, University of Sydney, Westmead, NSW 2145, Australia
| | - Katharina Gaus
- EMBL Australia Node in Single Molecule Science, School of Medical Sciences, University of New South Wales, Sydney, NSW 2052, Australia; ARC Centre of Excellence in Advanced Molecular Imaging, University of New South Wales, Sydney, NSW 2052, Australia
| | - Anthony J Cesare
- Genome Integrity Unit, Children's Medical Research Institute, University of Sydney, Westmead, NSW 2145, Australia.
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Chen J, Wei Y, Chen X, Jiao J, Zhang Y. Polyunsaturated fatty acids ameliorate aging via redox-telomere-antioncogene axis. Oncotarget 2018; 8:7301-7314. [PMID: 28038469 PMCID: PMC5352322 DOI: 10.18632/oncotarget.14236] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2016] [Accepted: 12/20/2016] [Indexed: 12/02/2022] Open
Abstract
Polyunsaturated fatty acids (PUFA), a group of nourishing and health-promoting nutrients, ameliorate age-related chronic diseases. However, how PUFA especially n-3 PUFA exert anti-aging functions remains poorly understood. Here we link fish oil, docosahexaenoic acid (DHA) and arachidonic acid (AA) to the aging etiology via a redox-telomere-antioncogene axis based on D-galactose-induced aging mice. Both fish oil and PUFA enhanced hepatic superoxide dismutase (SOD) and catalase activities and cardiac SOD activities within the range of 18%-46%, 26%-65% and 19%-58%, respectively, whereas reduced cerebral monoamine oxidase activity, plasma F2-isoprostane level and cerebral lipid peroxidation level by 56%-90%, 20%-79% and 16%-54%, respectively. Thus, PUFA improve the in vivo redox and oxidative stress induced aging process, which however does not exhibit a dose-dependent manner. Notably, both PUFA and fish oil effectively inactivated testicular telomerase and inhibited c-Myc-mediated telomerase reverse transcriptase expression, whereas n-3 PUFA rather than n-6 PUFA protected liver and testes against telomere shortening within the range of 13%-25% and 25%-27%, respectively. Therefore, n-3 PUFA may be better at inhibiting the DNA damage induced aging process. Surprisingly, only DHA significantly suppressed cellular senescence pathway evidenced by testicular antioncogene p16 and p53 expression. This work provides evident support for the crosstalk between PUFA especially n-3 PUFA and the aging process via maintaining the in vivo redox homeostasis, rescuing age-related telomere attrition and down-regulating the antioncogene expression.
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Affiliation(s)
- Jingnan Chen
- Department of Food Science and Nutrition, College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou, Zhejiang, China
| | - Yan Wei
- Department of Food Science and Nutrition, College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou, Zhejiang, China
| | - Xinyu Chen
- Department of Food Science and Nutrition, College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou, Zhejiang, China
| | - Jingjing Jiao
- Department of Nutrition, School of Public Health, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
| | - Yu Zhang
- Department of Food Science and Nutrition, College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou, Zhejiang, China
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Ray S, Bandaria JN, Qureshi MH, Yildiz A, Balci H. G-quadruplex formation in telomeres enhances POT1/TPP1 protection against RPA binding. Proc Natl Acad Sci U S A 2014; 111:2990-5. [PMID: 24516170 DOI: 10.1073/pnas.1321436111] [Citation(s) in RCA: 108] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Human telomeres terminate with a single-stranded 3' G overhang, which can be recognized as a DNA damage site by replication protein A (RPA). The protection of telomeres (POT1)/POT1-interacting protein 1 (TPP1) heterodimer binds specifically to single-stranded telomeric DNA (ssTEL) and protects G overhangs against RPA binding. The G overhang spontaneously folds into various G-quadruplex (GQ) conformations. It remains unclear whether GQ formation affects the ability of POT1/TPP1 to compete against RPA to access ssTEL. Using single-molecule Förster resonance energy transfer, we showed that POT1 stably loads to a minimal DNA sequence adjacent to a folded GQ. At 150 mM K(+), POT1 loading unfolds the antiparallel GQ, as the parallel conformation remains folded. POT1/TPP1 loading blocks RPA's access to both folded and unfolded telomeres by two orders of magnitude. This protection is not observed at 150 mM Na(+), in which ssTEL forms only a less-stable antiparallel GQ. These results suggest that GQ formation of telomeric overhangs may contribute to suppression of DNA damage signals.
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Han X, Liu D, Zhang Y, Li Y, Lu W, Chen J, Songyang Z. Akt regulates TPP1 homodimerization and telomere protection. Aging Cell 2013; 12:1091-9. [PMID: 23862686 DOI: 10.1111/acel.12137] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/10/2013] [Indexed: 12/01/2022] Open
Abstract
Telomeres are specialized structures at the ends of eukaryotic chromosomes that are important for maintaining genome stability and integrity. Telomere dysfunction has been linked to aging and cancer development. In mammalian cells, extensive studies have been carried out to illustrate how core telomeric proteins assemble on telomeres to recruit the telomerase and additional factors for telomere maintenance and protection. In comparison, how changes in growth signaling pathways impact telomeres and telomere-binding proteins remains largely unexplored. The phosphatidylinositol 3-kinase (PI3-K)/Akt (also known as PKB) pathway, one of the best characterized growth signaling cascades, regulates a variety of cellular function including cell proliferation, survival, metabolism, and DNA repair, and dysregulation of PI3-K/Akt signaling has been linked to aging and diseases such as cancer and diabetes. In this study, we provide evidence that the Akt signaling pathway plays an important role in telomere protection. Akt inhibition either by chemical inhibitors or small interfering RNAs induced telomere dysfunction. Furthermore, we found that TPP1 could homodimerize through its OB-fold, a process that was dependent on the Akt kinase. Telomere damage and reduced TPP1 dimerization as a result of Akt inhibition was also accompanied by diminished recruitment of TPP1 and POT1 to the telomeres. Our findings highlight a previously unknown link between Akt signaling and telomere protection.
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Affiliation(s)
- Xin Han
- Key Laboratory of Gene Engineering of the Ministry of Education; School of Life Sciences and Key Laboratory of Reproductive Medicine of Guangdong Province; the First Affiliated Hospital; Sun Yat-Sen University; Guangzhou Guangzhou China
| | - Dan Liu
- Verna and Marrs Mclean Department of Biochemistry and Molecular Biology; Baylor College of Medicine; One Baylor Plaza; Houston TX 77030 USA
| | - Yi Zhang
- Verna and Marrs Mclean Department of Biochemistry and Molecular Biology; Baylor College of Medicine; One Baylor Plaza; Houston TX 77030 USA
| | - Yujing Li
- Key Laboratory of Gene Engineering of the Ministry of Education; School of Life Sciences and Key Laboratory of Reproductive Medicine of Guangdong Province; the First Affiliated Hospital; Sun Yat-Sen University; Guangzhou Guangzhou China
| | - Weisi Lu
- Key Laboratory of Gene Engineering of the Ministry of Education; School of Life Sciences and Key Laboratory of Reproductive Medicine of Guangdong Province; the First Affiliated Hospital; Sun Yat-Sen University; Guangzhou Guangzhou China
| | - Junjie Chen
- Department of Experimental Radiation Oncology; The University of Texas M D Anderson Cancer Center; Houston TX 77030 USA
| | - Zhou Songyang
- Key Laboratory of Gene Engineering of the Ministry of Education; School of Life Sciences and Key Laboratory of Reproductive Medicine of Guangdong Province; the First Affiliated Hospital; Sun Yat-Sen University; Guangzhou Guangzhou China
- Verna and Marrs Mclean Department of Biochemistry and Molecular Biology; Baylor College of Medicine; One Baylor Plaza; Houston TX 77030 USA
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Morciano P, Zhang Y, Cenci G, Rong YS. A hypomorphic mutation reveals a stringent requirement for the ATM checkpoint protein in telomere protection during early cell division in Drosophila. G3 (Bethesda) 2013; 3:1043-8. [PMID: 23604076 DOI: 10.1534/g3.113.006312] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Using Drosophila as a model system, we identified a stringent requirement for the conserved function of Ataxia Telangiectasia Mutated (ATM) in telomere protection during early embryonic development. Animals homozygous for a hypomorphic mutation in atm develop normally with minimal telomere dysfunction. However, mutant females produce inviable embryos that succumb to mitotic failure caused by covalent fusions of telomeric DNA. Interestingly, although the atm mutation encodes a premature stop codon, it must not have eliminated the production of the mutant protein, and the mutant protein retains kinase activity upon DNA damage. Moreover, although the embryonic phenotype of this mutation resembles that of hypomorphic mutations in the MRN complex, the function of MRN appears normal in the atm embryos. In contrast, there is a prominent reduction of the level of HipHop, an essential member of the Drosophila capping complex. How ATM functions in telomere protection remains poorly understood. The amenability of Drosophila embryos to molecular and biochemical investigations ensures that this newly identified mutation will facilitate future studies of ATM in telomere maintenance.
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Raffa GD, Cenci G, Ciapponi L, Gatti M. Organization and Evolution of Drosophila Terminin: Similarities and Differences between Drosophila and Human Telomeres. Front Oncol 2013; 3:112. [PMID: 23675571 PMCID: PMC3650302 DOI: 10.3389/fonc.2013.00112] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2013] [Accepted: 04/24/2013] [Indexed: 11/16/2022] Open
Abstract
Drosophila lacks telomerase and fly telomeres are elongated by occasional transposition of three specialized retroelements. Drosophila telomeres do not terminate with GC-rich repeats and are assembled independently of the sequence of chromosome ends. Recent work has shown that Drosophila telomeres are capped by the terminin complex, which includes the fast-evolving proteins HOAP, HipHop, Moi, and Ver. These proteins, which are not conserved outside Drosophilidae and closely related Diptera, localize and function exclusively at telomeres, protecting them from fusion events. Other proteins required to prevent end-to-end fusion in flies include HP1, Eff/UbcD1, ATM, the components of the Mre11-Rad50-Nbs (MRN) complex, and the Woc transcription factor. These proteins do not share the terminin properties; they are evolutionarily conserved non-fast-evolving proteins that do not accumulate only at telomeres and do not serve telomere-specific functions. We propose that following telomerase loss, Drosophila rapidly evolved terminin to bind chromosome ends in a sequence-independent manner. This hypothesis suggests that terminin is the functional analog of the shelterin complex that protects human telomeres. The non-terminin proteins are instead likely to correspond to ancestral telomere-associated proteins that did not evolve as rapidly as terminin because of the functional constraints imposed by their involvement in diverse cellular processes. Thus, it appears that the main difference between Drosophila and human telomeres is in the protective complexes that specifically associate with the DNA termini. We believe that Drosophila telomeres offer excellent opportunities for investigations on human telomere biology. The identification of additional Drosophila genes encoding non-terminin proteins involved in telomere protection might lead to the discovery of novel components of human telomeres.
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Affiliation(s)
- Grazia D Raffa
- Istituto Pasteur-Fondazione Cenci Bolognetti, Sapienza Università di Roma Roma, Italy ; Dipartimento di Biologia e Biotecnologie "C. Darwin," Sapienza Università di Roma Roma, Italy
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