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A New View of the T-Loop Junction: Implications for Self-Primed Telomere Extension, Expansion of Disease-Related Nucleotide Repeat Blocks, and Telomere Evolution

Abstract:
Telomere loops (t-loops) are formed at the ends of chromosomes in species ranging from humans to worms, plants, and with genetic manipulation, some yeast. Recent in vitro studies demonstrated that transcription of telomeric DNA leads to highly efficient t-loop formation. It was also shown that both DNA termini are inserted into the preceding DNA to generate a highly stable t-loop junction. Furthermore, some telomeric RNA remains present at the junction, potentially acting as a plug to further protect and stabilize the t-loop. Modeling the loop junction reveals two mechanisms by which the canonical chromosomal replication factors could extend the telomere in the absence of telomerase. One mechanism would utilize the annealed 3’ terminus as a de novo replication origin. In vitro evidence for the ability of the t-loop to prime telomere extension using the T7 replication factors is presented. A second mechanism would involve resolution of the Holliday junction present in the t-loop bubble by factors such as GEN1 to generate a rolling circle template at the extreme terminus of the telomere. This could lead to large expansions of the telomeric tract. Here, we propose that telomeres evolved as terminal elements containing long arrays of short nucleotide repeats due to the ability of such arrays to fold back into loops and self-prime their replicative extension. In this view, telomerase may have evolved later to provide a more precise mechanism of telomere maintenance. Both pathways have direct relevance to the alternative lengthening of telomeres (ALT) pathway. This view also provides a possible mechanism for the very large repeat expansions observed in nucleotide repeat diseases such as Fragile X syndrome, myotonic dystrophy, familial amyotrophic lateral sclerosis (ALS), and frontotemporal dementia (FTD). The evolution of telomeres is discussed in the framework of these models.
Author Listing： Lubomir Tomaska;Jozef Nosek;Anirban Kar;Smaranda Willcox;Jack D. Griffith
Volume： 10
Pages： None
DOI： 10.3389/fgene.2019.00792
Language： English
Journal： Frontiers in Genetics

Frontiers in Genetics

FRONT GENET

影响因子：2.8
是否综述期刊：否
是否OA：是
是否预警：不在预警名单内
发行时间：-
ISSN：1664-8021
发刊频率：-
收录数据库：SCIE/Scopus收录/DOAJ开放期刊
出版国家/地区：UNITED STATES
出版社：Frontiers Media S.A.

期刊介绍

Frontiers in Genetics publishes rigorously peer-reviewed research on genes and genomes relating to all the domains of life, from humans to plants to livestock and other model organisms. Led by an outstanding Editorial Board of the world’s leading experts, this multidisciplinary, open-access journal is at the forefront of communicating cutting-edge research to researchers, academics, clinicians, policy makers and the public.The study of inheritance and the impact of the genome on various biological processes is well documented. However, the majority of discoveries are still to come. A new era is seeing major developments in the function and variability of the genome, the use of genetic and genomic tools and the analysis of the genetic basis of various biological phenomena.

《遗传学前沿》出版了严格的同行评审研究，涉及从人类到植物到牲畜和其他模式生物的所有生命领域的基因和基因组。由世界顶尖专家组成的杰出编辑委员会领导，这本多学科、开放获取的期刊走在前沿，向研究人员、学者、临床医生、政策制定者和公众传播尖端研究。遗传研究和基因组对各种生物过程的影响都有详细的文献记录。然而，大部分的发现还在后面。一个新的时代正在看到基因组的功能和可变性、遗传和基因组工具的使用以及对各种生物现象的遗传基础的分析方面的重大发展。

年发文量 1004
国人发稿量 581
国人发文占比 57.82%
自引率 3.6%
平均录取率 -
平均审稿周期 14 Weeks
版面费 -
偏重研究方向 Biochemistry, Genetics and Molecular Biology-Molecular Medicine
期刊官网 https://www.frontiersin.org/journals/genetics
投稿链接 https://www.frontiersin.org/submission/SubmissionHome.aspx?domainId=1&fieldId=30&specialtyId=0&entityType=1&entityId=240

质量指标占比

研究类文章占比 OA被引用占比 撤稿占比 出版后修正文章占比
88.55% 99.52% - -

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时间 预警情况
2025年03月发布的2025版 不在预警名单中
2024年02月发布的2024版 不在预警名单中
2023年01月发布的2023版 不在预警名单中
2021年12月发布的2021版 不在预警名单中
2020年12月发布的2020版 不在预警名单中

JCR分区 WOS分区等级：Q2区

版本 按学科 分区
WOS期刊SCI分区
（2021-2022年最新版）
GENETICS & HEREDITY Q2

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版本 大类学科 小类学科 Top期刊 综述期刊
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3区
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3区
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2021年12月
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3区
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2021年12月
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GENETICS & HEREDITY
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生物学
3区
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3区
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