Bollenbach Thomas J, Schuster Gadi, Stern David B
Boyce Thompson Institute for Plant Research, Tower Rd, Ithaca, New York 14853, USA.
Prog Nucleic Acid Res Mol Biol. 2004;78:305-37. doi: 10.1016/S0079-6603(04)78008-3.
Chloroplasts were acquired by eukaryotic cells through endosymbiosis and have retained their own gene expression machinery. One hallmark of chloroplast gene regulation is the predominance of posttranscriptional control, which is exerted both at the gene-specific and global levels. This review focuses on how chloroplast mRNA stability is regulated, through an examination of poly(A)-dependent and independent pathways. The poly(A)-dependent pathway is catalyzed by polynucleotide phosphorylase (PNPase), which both adds and degrades destabilizing poly(A) tails, whereas RNase II and PNPase may both participate in the poly(A)-independent pathway. Each system is initiated through endonucleolytic cleavages that remove 3' stem-loop structures, which are catalyzed by the related proteins CSP41a and CSP41b and possibly an RNase E-like enzyme. Overall, chloroplasts have retained the prokaryotic endonuclease-exonuclease RNA degradation system despite evolution in the number and character of the enzymes involved. This reflects the presence of the chloroplast within a eukaryotic host and the complex responses that occur to environmental and developmental cues.
叶绿体是真核细胞通过内共生获得的，并且保留了自身的基因表达机制。叶绿体基因调控的一个标志是转录后控制占主导地位，这在基因特异性和全局水平上都有体现。本综述通过研究依赖多聚腺苷酸（poly(A)）和不依赖多聚腺苷酸的途径，聚焦于叶绿体mRNA稳定性是如何被调控的。依赖多聚腺苷酸的途径由多核苷酸磷酸化酶（PNPase）催化，该酶既能添加又能降解不稳定的多聚腺苷酸尾巴，而核糖核酸酶II（RNase II）和PNPase可能都参与不依赖多聚腺苷酸的途径。每个系统都是通过核酸内切酶切割起始的，这些切割去除3'茎环结构，这是由相关蛋白CSP41a和CSP41b以及可能的一种类似核糖核酸酶E的酶催化的。总体而言，尽管参与的酶在数量和特性上有所进化，但叶绿体仍保留了原核生物的核酸内切酶-核酸外切酶RNA降解系统。这反映了叶绿体存在于真核宿主中以及对环境和发育信号所发生的复杂反应。
