Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA.
Science. 2010 Sep 10;329(5997):1355-8. doi: 10.1126/science.1192272.
Many bacteria and archaea contain clustered regularly interspaced short palindromic repeats (CRISPRs) that confer resistance to invasive genetic elements. Central to this immune system is the production of CRISPR-derived RNAs (crRNAs) after transcription of the CRISPR locus. Here, we identify the endoribonuclease (Csy4) responsible for CRISPR transcript (pre-crRNA) processing in Pseudomonas aeruginosa. A 1.8 angstrom crystal structure of Csy4 bound to its cognate RNA reveals that Csy4 makes sequence-specific interactions in the major groove of the crRNA repeat stem-loop. Together with electrostatic contacts to the phosphate backbone, these enable Csy4 to bind selectively and cleave pre-crRNAs using phylogenetically conserved serine and histidine residues in the active site. The RNA recognition mechanism identified here explains sequence- and structure-specific processing by a large family of CRISPR-specific endoribonucleases.
许多细菌和古菌含有成簇规律间隔短回文重复序列（CRISPRs），这些重复序列赋予了它们对入侵遗传元件的抗性。该免疫系统的核心是在转录 CRISPR 基因座后产生 CRISPR 衍生的 RNA（crRNA）。在这里，我们鉴定了负责铜绿假单胞菌 CRISPR 转录本（前 crRNA）加工的内切核酸酶（Csy4）。与同源 RNA 结合的 Csy4 的 1.8 埃晶体结构表明，Csy4 在 crRNA 重复茎环的大沟中形成序列特异性相互作用。与磷酸骨架的静电接触一起，这些使 Csy4 能够使用活性位点中进化上保守的丝氨酸和组氨酸残基选择性地结合并切割前 crRNA。此处鉴定的 RNA 识别机制解释了一大类 CRISPR 特异性内切核糖核酸酶的序列和结构特异性加工。
