Choquet Y, Stern D B, Wostrikoff K, Kuras R, Girard-Bascou J, Wollman F A
Unité Propre de Recherche 9072/Centre National de la Recherche Scientifique, Institut de Biologie Physico-Chimique, 13, rue P. et M. Curie, 75005 Paris, France.
Proc Natl Acad Sci U S A. 1998 Apr 14;95(8):4380-5. doi: 10.1073/pnas.95.8.4380.
A process that we refer to as control by epistasy of synthesis (CES process) occurs during chloroplast protein biogenesis in Chlamydomonas reinhardtii: the synthesis of some chloroplast-encoded subunits, the CES subunits, is strongly attenuated when some other subunits from the same complex, the dominant subunits, are missing. Herein we investigate the molecular basis of the CES process for the biogenesis of the cytochrome b6f complex and show that negative autoregulation of cytochrome f translation occurs in the absence of other complex subunits. This autoregulation is mediated by an interaction, either direct or indirect, between the 5' untranslated region of petA mRNA, which encodes cytochrome f, and the C-terminal domain of the unassembled protein. This model for the regulation of cytochrome f translation explains both the decreased rate of cytochrome f synthesis in vivo in the absence of its assembly partners and its increase in synthesis when significant accumulation of the C-terminal domain of the protein is prevented. When expressed from a chimeric mRNA containing the atpA 5' untranslated region, cytochrome f no longer showed an assembly-dependent regulation of translation. Conversely, the level of antibiotic resistance conferred by a chimeric petA-aadA-rbcL gene was shown to depend on the state of assembly of cytochrome b6f complexes and on the accumulation of the C-terminal domain of cytochrome f. We discuss the possible ubiquity of the CES process in organellar protein biogenesis.
在莱茵衣藻叶绿体蛋白质生物合成过程中会发生一个我们称为合成上位控制（CES过程）的过程：当同一复合物中的其他一些亚基（主导亚基）缺失时，一些叶绿体编码的亚基（CES亚基）的合成会受到强烈抑制。在此，我们研究了细胞色素b6f复合物生物合成中CES过程的分子基础，并表明在没有其他复合物亚基的情况下，细胞色素f的翻译会发生负自调控。这种自调控是由编码细胞色素f的petA mRNA的5'非翻译区与未组装蛋白的C末端结构域之间直接或间接的相互作用介导的。这种细胞色素f翻译调控模型既解释了在没有其组装伙伴的情况下，细胞色素f在体内合成速率降低的现象，也解释了在阻止该蛋白C末端结构域大量积累时其合成增加的现象。当从含有atpA 5'非翻译区的嵌合mRNA表达时，细胞色素f不再表现出翻译的组装依赖性调控。相反，嵌合petA-aadA-rbcL基因赋予的抗生素抗性水平显示取决于细胞色素b6f复合物的组装状态以及细胞色素f C末端结构域的积累情况。我们讨论了CES过程在细胞器蛋白质生物合成中可能的普遍性。
