Anti-cas spacers in orphan CRISPR4 arrays prevent uptake of active CRISPR-Cas I-F systems
Anti-cas spacers in orphan CRISPR4 arrays prevent uptake of active CRISPR-Cas I-F systems
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DOI：
10.1038/nmicrobiol.2016.81
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发表时间：
2016-08-01
影响因子：
28.3
通讯作者：
Mojica, Francisco J. M.
中科院分区：
文献类型：
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作者：
Almendros, Cristobal;Guzman, Noemi M.;Mojica, Francisco J. M.
古生菌和细菌聚集在规则间隔的短回文重复序列(CRISPR)基因座上。这些阵列编码RNA分子(CrRNA)，每个分子包含一个单一重复间隔序列。CrRNAs引导CRISPR相关(CAS)蛋白裂解与crRNA间隔区互补的核酸，从而干扰靶向外源成分。值得注意的是，预先存在的间隔区可以通过启动的适应机制触发从目标分子获得新的间隔区。在这里，我们展示了自然产生的孤儿CRISPR阵列，其包含与同源(缺失)CAS基因序列匹配的间隔区，能够引起启动适应和对携带这些基因的遗传元件的直接干扰。我们的发现表明，存在一种防止全装备CRISPR-CAS系统转移的抗CAS机制。因此，他们认为CRISPR免疫可能是特定原核生物所不希望的，可能是因为它们可能限制通过侧向转移获得有利序列的可能性。
Archaea and bacteria harbour clustered regularly interspaced short palindromic repeats (CRISPR) loci. These arrays encode RNA molecules (crRNA), each containing a sequence of a single repeat-intervening spacer. The crRNAs guide CRISPR-associated (Cas) proteins to cleave nucleic acids complementary to the crRNA spacer, thus interfering with targeted foreign elements. Notably, pre-existing spacers may trigger the acquisition of new spacers from the target molecule by means of a primed adaptation mechanism. Here, we show that naturally occurring orphan CRISPR arrays that contain spacers matching sequences of the cognate (absent) cas genes are able to elicit both primed adaptation and direct interference against genetic elements carrying those genes. Our findings show the existence of an anti-cas mechanism that prevents the transfer of a fully equipped CRISPR-Cas system. Hence, they suggest that CRISPR immunity may be undesired by particular prokaryotes, potentially because they could limit possibilities for gaining favourable sequences by lateral transfer.