Novel CRISPR systems capable of cleaving both DNA and RNA are progressively emerging as attractive tools for genome manipulation of prokaryotic and eukaryotic organisms. We report specific characteristics of CRISPR systems present in Oxynema aestuarii AP17, a halotolerant, filamentous cyanobacterium and the second known member of the Oxynema genus. In-silico analyses of its whole-genome sequence revealed the presence of multiple Type I and Type III CRISPR loci with one Type I-G system previously unreported in cyanobacteria. We further identified the leader sequences at the 5′ end of multiple CRISPR loci, many of which were distinct from previously reported cyanobacterial CRISPR leaders. Phylogenetic analyses of the O. aestuarii AP17 Cas1 proteins revealed two protein sequences that were unique and distantly related to other cyanobacterial Cas1 protein sequences. Our findings are significant because novel Class 1 CRISPR systems possess multi-subunit effectors and are highly flexible for repurposing by protein domain fusions made to the effector complex. Additionally, Type III CRISPRs are particularly useful for genome editing in certain extremophiles for which mesophilic Type II CRISPRs are ineffective.

中文翻译：

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耐盐丝状红树林蓝细菌的计算机全基因组序列分析揭示了具有独特特性的 CRISPR-Cas 系统

能够切割 DNA 和 RNA 的新型 CRISPR 系统正逐渐成为原核和真核生物基因组操作的有吸引力的工具。我们报告了Oxynema aestuarii AP17 中存在的 CRISPR 系统的具体特征，Oxynema aestuarii AP17 是一种耐盐丝状蓝细菌，也是Oxynema属的第二个已知成员。对其全基因组序列的计算机分析揭示了多个 I 型和 III 型 CRISPR 位点的存在，以及一个先前未在蓝细菌中报道的 IG 型系统。我们进一步鉴定了多个 CRISPR 位点 5' 端的前导序列，其中许多序列与之前报道的蓝藻 CRISPR 前导序列不同。对O. aestuarii AP17 Cas1 蛋白的系统发育分析揭示了两个独特的蛋白序列，并且与其他蓝藻 Cas1 蛋白序列有较远的相关性。我们的研究结果意义重大，因为新型 1 类 CRISPR 系统拥有多亚基效应子，并且通过与效应子复合物进行蛋白质结构域融合而高度灵活地重新利用。此外，III 型 CRISPR 对于某些嗜温 II 型 CRISPR 无效的极端微生物的基因组编辑特别有用。