7月18日,，GENE DEV雜志在線報(bào)道,，在被子植物中科學(xué)家發(fā)現(xiàn)不同于以往認(rèn)識(shí)的鈍性末端端粒保護(hù)結(jié)構(gòu)。
單鏈端粒DNA突出結(jié)構(gòu),，被認(rèn)為是進(jìn)化上保守的基本結(jié)構(gòu)元件,，發(fā)揮保護(hù)染色體末端的重要功能。以前人們認(rèn)為,，此DNA突出結(jié)構(gòu)在端粒部位的形成,，由前導(dǎo)鏈機(jī)制復(fù)制導(dǎo)致。此過程涉及一種機(jī)制尚不清楚的DNA復(fù)制后鈍性末端處理,。
出乎意料的是,，本研究發(fā)現(xiàn)，被子植物包含鈍性末端和短的（1 - 3個(gè)核苷酸）包含G核苷的突出端粒結(jié)構(gòu),，這些結(jié)構(gòu)可穩(wěn)定保留在有絲分裂后組織中,。從而揭示了一種新的，保護(hù)染色體末端的機(jī)制,。
平末端端粒的完整性取決于Ku70/80異二聚體,，但不是在另一個(gè)端粒封蓋蛋白，STN1,。奇怪的是,，缺失Ku蛋白的端粒是功能完好的。這些端粒被核酸外切酶1切割，從而促進(jìn)染色單體內(nèi)重組,，這可能有助于形成替代的染色體末端封蓋結(jié)構(gòu)。
這些數(shù)據(jù)質(zhì)疑這樣的觀點(diǎn),，即認(rèn)為端粒需要單鏈DNA突起形成一個(gè)功能性的封蓋結(jié)構(gòu),，并證明在染色體末端的保護(hù)問題上，大自然有著靈活的解決方案,。（生物谷bioon.com）
doi:10.1016/j.cell.2011.10.017
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Chromosome end protection by blunt-ended telomeres
Anita Kazda,Barbara Zellinger1,Max R?ssler1,Elisa Derboven1,Branislav Kusenda andKarel Riha
Single-stranded telomeric DNA protrusions are considered to be evolutionarily conserved structural elements essential for chromosome end protection. Their formation at telomeres replicated by the leading strand mechanism is thought to involve poorly understood post-replicative processing of blunt ends. Unexpectedly, we found that angiosperm plants contain blunt-ended and short (1- to 3-nucleotide) G-overhang-containing telomeres that are stably retained in post-mitotic tissues, revealing a novel mechanism of chromosome end protection. The integrity of blunt-ended telomeres depends on the Ku70/80 heterodimer but not on another telomere capping protein, STN1. Curiously, Ku-depleted telomeres are fully functional. They are resected by exonuclease 1, promoting intrachromatid recombination, which may facilitate formation of an alternative capping structure. These data challenge the view that telomeres require ssDNA protrusions for forming a functional capping structure and demonstrate flexibility in solutions to the chromosome end protection problem.
