Real-time dynamics of CRISPR visualized by high-speed atomic force microscopy
Pretty cool visualization.  Single molecule work like that is challenging to do properly - but when done properly gives a kind of visual proof to a hypothesis that is hard to controvert. Wild-type Cas9 cuts genomic DNA, and when it does, the strand can go flying - with repair a possibility rather than an inevitability.<p>Cas9 (and similar proteins) have 2 basic functions:<p>1) to bind to specific DNA (by means of complementing a specifically-bound RNA)<p>2) to cut the DNA that is has bound.<p>Only one of these functions is actually desirable or unique to Cas9 - that of binding to a sequence-specific part of DNA.  The &#x27;cutting&#x27; function is how the CRISPR system naturally destroys foreign DNA in Cas9&#x27;s normal environment, but is generally not desirable in these synthetic biology or therapeutic applications.  For genetic engineering purposes we really have better tools than Cas9 to cut, modify, or otherwise affect DNA - but Cas9 is clearly a fantastic tool to <i>localize</i> to particular sequences.  That this paper so clearly demonstrates the terrifying damage that cleavage can do to genomic DNA only reinforces that Cas9 is a useful scaffold upon which to engineer further tools, but in its wild-type form is kind of scary.<p>Recent papers from the Liu lab at Harvard [1] (among many others) show how you can edit DNA using a modified Cas9 that has been modified to <i>not</i> have that second cutting function, while retaining the ability to bind to a specific DNA sequence. The synthetic &quot;BaseEditor&quot; protein has been further modified to have more complicated DNA <i>modification</i> capabilities, rather than whole-sale slicing of DNA [2]. Though this designed protein with Cas9 at its core is complicated, it should not cleave and let dangle genomic DNA as we see it here visualized.  I&#x27;d be curious to see how the BaseEditors behave under a similar visualization.<p>[1] Kim et al. 2017: <a href="https:&#x2F;&#x2F;www.nature.com&#x2F;articles&#x2F;nbt.3803" rel="nofollow">https:&#x2F;&#x2F;www.nature.com&#x2F;articles&#x2F;nbt.3803</a><p>[2] BaseEditor v4: <a href="https:&#x2F;&#x2F;serotiny.bio&#x2F;notes&#x2F;proteins&#x2F;sabe4gam&#x2F;" rel="nofollow">https:&#x2F;&#x2F;serotiny.bio&#x2F;notes&#x2F;proteins&#x2F;sabe4gam&#x2F;</a>