字幕列表 影片播放 列印英文字幕 You’ve probably heard of CRISPR technologies and their much-discussed ability to edit our DNA. For the most part, these stories probably refer to CRISPR-Cas9. But a new system, CRISPR-Cas3, has just been used in human cells for the very first time...and offers a whole new set of tools that could have huge implications for curing previously incurable viruses. To review, CRISPR-Cas9 is the combination of a custom-made piece of RNA (that’s the clustered regularly interspersed palindromic repeats, or the CRISPR part) and an enzyme (that’s the CRISPR associated protein 9, or Cas-9 part). The RNA is engineered to recognize a certain segment of DNA, which guides the CRISPR-Cas9 system to that section so it can then cut and delete, or potentially add to, or even replace with an altered version. CRISPR-Cas9 belongs to a family of CRISPR-based editing tools called Class 2 systems. There are actually three classes of CRISPR-Cas systems, most of them belonging to classes one and two. CRISPR-Cas3 is a Class 1 system. Class 1 systems are apparently more prevalent in our biological processes and are more sophisticated than Class 2 systems, but have so far they’ve only been used experimentally as gene editing tools in bacteria and archaea. CRISPR-Cas3 has the unique capability to search for, identify, and delete much longer stretches of DNA than CRISPR-Cas9, chunks up to 100,000 base pairs long—and it makes multiple cuts along that chunk, kind of like a shredder. A research team that recently demonstrated this in human cells for the first time--in a petri dish--believes the Cas3 system could be a better option than Cas9 because it uses a longer guide RNA sequence. This means it’s better at more accurately locating the chunk we want to target. This makes it ideal for editing non-coding segments of our genome. These are pieces of our DNA, about 98% of it, actually, that don’t directly correlate to something. Instead they act as regulators, determining how much that gene is expressed, if at all. We don’t have a great understanding of what this huge swathe of our DNA really does, so using CRISPR-Cas3 to delete large sections and then seeing what happens, in a lab setting of course, could give us a much better understanding of what these non-coding sections do and how they work. CRISPR-Cas3 could also delete sections of genes that have been permanently altered by viruses. Diseases like herpes actually hijack our DNA, inserting their sequences into our genome to use our cell’s machinery to make their own often malicious proteins. Herpes in particular is spectacularly good at avoiding our immune system and goes through dormant stages, making it impossible to cure. But its permanent alterations of our DNA could make it vulnerable to attack by CRISPR technologies, and CRISPR-Cas3’s accurate targeting and powerful shredding capabilities could knock it out of our system for good. Some other teams are pointing to CRISPR-Cas3 as a potential solution for antibiotic-resistant bacteria. Instead of deleting a sequence of DNA infected by a virus’ DNA, CRISPR-Cas3 could just chew up the bacterium’s whole genome beyond the point of repair, causing the organism’s death—no antibiotics required! So, CRISPR-Cas3 has the potential to delete large chunks of our DNA, proving useful and potentially more efficient and cost-effective in some essential medical situations—but we still have to learn how to control it. While the most recent study into CRISPR-Cas3’s potential did demonstrate that we can use it in human cells, we still don’t have total control over how long a section we tell it to delete. And of course, since we’re not even entirely sure of the complete function of most of our genes, we would want to make sure the stuff we’re deleting is, y’know...safe to delete. Or that we have a healthy version to replace it with, some kind of backup plan. There are all kinds of new studies coming out about the unexpected effects of CRISPR-Cas9— deletions we didn’t mean to make and didn’t see coming—so with all of this gene-editing stuff we’ll need to proceed with extreme caution and many more years of experimentation before we see this in a clinical setting. But this new exploration of CRISPR-Cas3’s potential is an exciting first proof-of-concept for a technology that could one day provide a solution for previously incurable viruses. If you want to learn more about viruses, you should check out our new show, Sick. It's all about what's happening in your body when things start to go wrong. We're talking Lyme disease, measles, lupus, and more. Is there a disease or illness you want us to cover? Let us know down in the comments. Make sure to subscribe to get all your science news. Thanks for watching.
B1 中級 新的CRISPR工具,可以從我們的DNA中 "刪除 "疾病。 (The New CRISPR Tool That Could ‘Delete’ Disease From Our DNA) 11 1 林宜悉 發佈於 2021 年 01 月 14 日 更多分享 分享 收藏 回報 影片單字