Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China.
University of Chinese Academy of Sciences, Beijing 100049, China.
Plant Cell. 2019 Jun;31(6):1308-1327. doi: 10.1105/tpc.18.00946. Epub 2019 Apr 8.
A key characteristic of chloroplast gene expression is the predominance of posttranscriptional control via numerous nucleus-encoded RNA binding factors. Here, we explored the essential roles of the S1-domain-containing protein ()/ Stabilizing Factor (BSF) in the stabilization and translation of chloroplast mRNAs. BSF binds to the intergenic region of -, thereby stabilizing 3' processed transcripts and stimulating translation. BSF also binds to the 5' untranslated region of and activates its translation. BSF displayed nucleic-acid-melting activity in vitro, and its absence induces structural changes to target RNAs in vivo, suggesting that BSF functions as an RNA chaperone to remodel RNA structure. BSF physically interacts with the pentatricopeptide repeat protein Chloroplast RNA Processing 1 (AtCRP1) and the ribosomal release factor-like protein Peptide chain Release Factor 3 (PrfB3), whose established RNA ligands overlap with those of BSF. In addition, PrfB3 stimulated the RNA binding ability of BSF in vitro. We propose that BSF and PrfB3 cooperatively reduce the formation of secondary RNA structures within target mRNAs and facilitate AtCRP1 binding. The translation activation function of BSF for is conserved in Arabidopsis () and maize (), but that for operates specifically in Arabidopsis. Our study sheds light on the mechanisms by which RNA binding proteins cooperatively regulate mRNA stability and translation in chloroplasts.
叶绿体基因表达的一个主要特征是通过大量核编码的 RNA 结合因子进行转录后调控。在这里，我们探讨了 S1 结构域蛋白 ()/ 稳定因子 (BSF) 在稳定和翻译叶绿体 mRNA 中的重要作用。BSF 与 - 基因间区结合，从而稳定 3' 加工的转录物并刺激翻译。BSF 还与 5' 非翻译区结合并激活其翻译。BSF 在体外具有核酸解链活性，其缺失会诱导体内靶 RNA 发生结构变化，表明 BSF 作为 RNA 伴侣发挥作用，重塑 RNA 结构。BSF 与五肽重复蛋白叶绿体 RNA 加工 1 (AtCRP1) 和核糖体释放因子样蛋白肽链释放因子 3 (PrfB3) 发生物理相互作用，其已建立的 RNA 配体与 BSF 的 RNA 配体重叠。此外，PrfB3 在体外刺激 BSF 的 RNA 结合能力。我们提出 BSF 和 PrfB3 协同作用，减少靶 mRNA 中二级 RNA 结构的形成，并促进 AtCRP1 结合。BSF 对 的翻译激活功能在拟南芥和玉米中保守，但对 的功能则在拟南芥中特异性发挥。我们的研究揭示了 RNA 结合蛋白如何协同调节叶绿体中 mRNA 稳定性和翻译的机制。
