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无序列依赖性的内源性/外源性分子响应规律间隔成簇短回文重复序列介导的转录调控体系

Sequence-Independent CRISPR-Based Transcription Regulators Responding Endogenous and Exogenous Molecules

  • 摘要: 规律间隔成簇短回文重复序列介导的转录调控(CRISPR-TRs)可以靶向任何目标基因来实现激活或抑制,在合成生物学领域引发了革命性变革. 然而,目前大多数诱导性CRISPR-TRs受序列依赖性限制,在遗传工程中的应用灵活性和可控性不足. 本文提出了一种策略:即构建无序列依赖性的CRISPR-TRs,这是通过利用sgRNA的茎环2结构设计实现的. 在该策略下,利用了内源性小分子(miR-20a和TK1 mRNA)和桥连RNA(bRNA)之间的立足点介导链替换反应来连接bRNA与sgRNA, 从而实现了VP64和p65-HSF1的协同转录激活,以响应内源性小分子. 为了响应外源性分子,通过在sgRNA的5'端添加响应序列和bRNA序列来封闭sgRNA的活性,通过剪切响应序列来实现sgRNA的激活. 这种方式被称为序列不受限互锁. 与传统序列受限互锁(间隔区屏蔽发夹)相比,使用序列不受限互锁的CRISPR-TR在响应和未响应Cas6A蛋白下的转录激活比值提高了2.28倍. 本工作展示了一种模块化且多用途的框架,用于哺乳动物细胞中的内源性和外源性分子响应型CRISPR-TRs的构建,而且无需受序列依赖性的限制.

     

    Abstract: CRISPR-based transcription regulators (CRISPR-TRs) have revolutionized the field of synthetic biology by enabling targeted activation or repression of any desired gene. However, the majority of existing inducible CRISPR-TRs are limited by their dependence on specific sequences, which restricts their flexibility and controllability in genetic engineering applications. In this study, we proposed a novel strategy to construct sequence-independent inducible CRISPR-TRs, which is achieved by the design of stem loop 2 in the single guide RNA (sgRNA). Under this strategy, by utilizing toehold-mediated strand displacement (TMSD) reactions between small endogenous molecules (miR-20a and TK1 mRNA) and bridge RNA (bRNA) to link bRNA with sgRNA, we achieved synergistic transcriptional activation of VP64 and p65-HSF1 in response to endogenous molecules. To enable response to exogenous molecules, we added response sequences and bRNA sequences to the 5' end of sgRNA to block sgRNA activity, and achieved activation of sgRNA by shearing the response sequence, called sequential unlimited interlocking (SUI). Compared with conventional sequence-restricted interlocking (spacer-blocking hairpin (SBH)), the transcriptional activation ratio between response and non-response to the Cas6A protein using our approach was increased by 2.28-fold. Our work presents a modular and versatile framework for endogenous and exogenous molecule-responsive CRISPR-TRs in mammalian cells, without limitations imposed by sequence dependence.

     

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