CRISPR, the genome editing tool, makes it easier to target and cut DNA than ever before, but one of its shortcomings is that it can9t cut just anywhere. New research has discovered a way to improve the tool and make it more versatile. The human genome has 3.2 billion bases of DNA. The most common form of CRISPR relies on a stretch of RNA to guide its molecular scissors—an enzyme called Cas9 in shorthand—to cut a specific one of those 3.2 billion bases. But Cas9 can9t latch onto the genome unless there is a specific sequence flanking the cut site, which amounts to something of a landing pad. Harvard University chemist David Liu and colleagues, as they report online in the 28 February issue of Nature , have engineered a new version of Cas9 that has a more commonly found DNA sequence and can land in four times as many places. Dubbed xCas9, it has only been tested on a few dozen sites so far, but it holds the promise of making the remarkably powerful CRISPR even more muscular. And, to the astonishment of Liu, the more promiscuous xCas9 in his lab9s experiments also had fewer off-target cuts than Cas9, which means it was less likely to introduce mistakes that could be dangerous when CRISPR is used for medicine.

中文翻译：

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基因组编辑器变得更加通用和精确

CRISPR，基因组编辑工具，比以往任何时候都更容易靶向和切割 DNA，但它的缺点之一是它不能在任何地方切割。新的研究发现了一种改进工具并使其更加通用的方法。人类基因组有 32 亿个 DNA 碱基。最常见的 CRISPR 形式依赖于一段 RNA 来引导其分子剪刀——一种简称为 Cas9 的酶——切割这 32 亿个碱基中的一个特定碱基。但是 Cas9 不能锁定到基因组上，除非在切割位点两侧有一个特定的序列，这相当于某种着陆垫。哈佛大学化学家 David Liu 及其同事在 2 月 28 日的《自然》杂志在线报道，他们设计了一种新版本的 Cas9，它具有更常见的 DNA 序列，并且可以在四倍的地方着陆。被称为 xCas9，到目前为止，它只在几十个站点上进行了测试，但它有望使非常强大的 CRISPR 变得更加强大。而且，令刘惊讶的是，他实验室 9 实验中更混杂的 xCas9 也比 Cas9 具有更少的脱靶切割，这意味着当 CRISPR 用于医学时，它不太可能引入可能造成危险的错误。