GENE DEV:钝性末端端粒亦可保护染色体末端

7月18日，<em>GENE DEV</em>杂志在线报道，在被子植物中科学家发现不同于以往认识的钝性末端端粒保护结构。

单链端粒DNA突出结构，被认为是进化上保守的基本结构元件，发挥保护染色体末端的重要功能。以前人们认为，此DNA突出结构在端粒部位的形成，由前导链机制复制导致。此过程涉及一种机制尚不清楚的DNA复制后钝性末端处理。

<!--more-->

出乎意料的是，本研究发现，被子植物包含钝性末端和短的（1 - 3个核苷酸）包含G核苷的突出端粒结构，这些结构可稳定保留在有丝分裂后组织中。从而揭示了一种新的，保护染色体末端的机制。

平末端端粒的完整性取决于Ku70/80异二聚体，但不是在另一个端粒封盖蛋白，STN1。奇怪的是，缺失Ku蛋白的端粒是功能完好的。这些端粒被核酸外切酶1切割，从而促进染色单体内重组，这可能有助于形成替代的染色体末端封盖结构。

这些数据质疑这样的观点，即认为端粒需要单链DNA突起形成一个功能性的封盖结构，并证明在染色体末端的保护问题上，大自然有着灵活的解决方案。 
<div id="ztload">
<div>
<div>

<img src="http://www.bioon.com/biology/UploadFiles/201207/2012072311230517.gif" alt="" width="113" height="149" border="0" hspace="0" />

<a title="" href="http://dx.doi.org/10.1016/j.cell.2011.10.017" target="_blank">doi:</a><a title="" href="http://genesdev.cshlp.org/content/early/2012/07/18/gad.194944.112.abstract" target="_blank">10.1016/j.cell.2011.10.017</a>
PMC:
PMID:

</div>
<div>

<br/><strong>Chromosome end protection by blunt-ended telomeres</strong><br/>


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.

<br/>来源：生物谷

</div>
</div>
</div>