CRISPR-Cas adaptive immune systems in bacteria and archaea utilize short CRISPR RNAs (crRNAs) to guide sequence-specific recognition and clearance of foreign genetic material. Multiple crRNAs are stored together in a compact format called a CRISPR array that is transcribed and processed into the individual crRNAs. While the exact processing mechanisms vary widely, some CRISPR-Cas systems, including those encoding the Cas9 nuclease, rely on a trans-activating crRNA (tracrRNA). The tracrRNA was discovered in 2011 and was quickly co-opted to create single-guide RNAs as core components of CRISPR-Cas9 technologies. Since then, further studies have uncovered processes extending beyond the traditional role of tracrRNA in crRNA biogenesis, revealed Cas nucleases besides Cas9 that are dependent on tracrRNAs, and established new applications based on tracrRNA engineering. In this review, we describe the biology of the tracrRNA and how its ongoing characterization has garnered new insights into prokaryotic immune defense and enabled key technological advances.

中文翻译：

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CRISPR 生物学和技术中的 tracrRNA。


细菌和古细菌中的 CRISPR-Cas 适应性免疫系统利用短 CRISPR RNA (crRNA) 来指导外源遗传物质的序列特异性识别和清除。多个 crRNA 以紧凑的格式存储在一起，称为 CRISPR 阵列，该阵列被转录并加工成单个 crRNA。虽然确切的处理机制差异很大，但一些 CRISPR-Cas 系统（包括编码 Cas9 核酸酶的系统）依赖于反式激活 crRNA (tracrRNA)。 tracrRNA 于 2011 年被发现，并很快被用来创建单引导 RNA 作为 CRISPR-Cas9 技术的核心组件。此后，进一步的研究揭示了 tracrRNA 在 crRNA 生物合成中的传统作用之外的过程，揭示了除 Cas9 之外依赖于 tracrRNA 的 Cas 核酸酶，并建立了基于 tracrRNA 工程的新应用。在这篇综述中，我们描述了 tracrRNA 的生物学特性，以及它的持续表征如何获得对原核免疫防御的新见解并实现关键技术进步。