Site-specific binding of a PPR protein defines and stabilizes 5′ and 3′ mRNA termini in chloroplasts
Site-specific binding of a PPR protein defines and stabilizes 5′ and 3′ mRNA termini in chloroplasts
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DOI：
10.1038/emboj.2009.121
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发表时间：
2009-07-22
期刊：
影响因子：
11.4
通讯作者：
Barkan, Alice
中科院分区：
文献类型：
--
作者：
Pfalz, Jeannette;Bayraktar, Omer Ali;Barkan, Alice
叶绿体mRNA群体的特征是由多顺反子前体加工产生的重叠转录本。这些加工事件的机制和功能意义尚不清楚。我们描述了一种五肽重复（PPR）蛋白，PPR10，其结合定义了玉米叶绿体中两个转录单位衍生的mRNA片段。PPR10在体内和体外与两个序列相似的基因间RNA区域相互作用。经过加工的5‘和3’ RNA末端在这些区域重叠了大约25个核苷酸。PPR10结合位点精确地映射到这些重叠序列上，并且PPR10对于具有这些末端的rna的积累是特别需要的。这些发现表明PPR10可以作为RNA从5‘或3’方向衰变的屏障，并且结合蛋白可以替代RNA发夹作为3'外切酶的屏障。结果表明，5′端和3′端的蛋白质“帽”可以定义叶绿体mRNA片段的末端。这些结果，加上最近对细菌RNA衰变的见解，为叶绿体转录物群体的生物发生和叶绿体mRNA稳定性的决定因素提供了一个统一的模型。EMBO杂志（2009）28,2042-2052。doi: 10.1038 / emboj.2009.121;2009年5月7日在线发布
Chloroplast mRNA populations are characterized by overlapping transcripts derived by processing from polycistronic precursors. The mechanisms and functional significance of these processing events are poorly understood. We describe a pentatricopeptide repeat (PPR) protein, PPR10, whose binding defines mRNA segments derived from two transcription units in maize chloroplasts. PPR10 interacts in vivo and in vitro with two intergenic RNA regions of similar sequence. The processed 5' and 3' RNA termini in these regions overlap by approximately 25 nucleotides. The PPR10-binding sites map precisely to these overlapping sequences, and PPR10 is required specifically for the accumulation of RNAs with these termini. These findings show that PPR10 serves as a barrier to RNA decay from either the 5' or 3' direction and that a bound protein provides an alternative to an RNA hairpin as a barrier to 3' exonucleases. The results imply that protein 'caps' at both 5' and 3' ends can define the termini of chloroplast mRNA segments. These results, together with recent insights into bacterial RNA decay, suggest a unifying model for the biogenesis of chloroplast transcript populations and for the determinants of chloroplast mRNA stability. The EMBO Journal (2009) 28, 2042-2052. doi: 10.1038/emboj.2009.121; Published online 7 May 2009