State Key Laboratory of Plant Genomics and National Center for Plant Gene Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China; Guangdong Provincial Key Laboratory for Plant Epigenetics, College of Life Sciences and Oceanography, Shenzhen University, Shenzhen 518060, China; Department of Botany and Plant Sciences, Institute of Integrative Genome Biology, University of California, Riverside, Riverside, CA 92521, USA.
State Key Laboratory of Plant Genomics and National Center for Plant Gene Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China; College of Life Sciences, University of Chinese Academy of Sciences, Beijing 100039, China.
Mol Plant. 2021 Feb 1;14(2):223-236. doi: 10.1016/j.molp.2020.10.006. Epub 2020 Oct 15.
Ribosome biogenesis, which takes place mainly in the nucleolus, involves coordinated expression of pre-ribosomal RNAs (pre-rRNAs) and ribosomal proteins, pre-rRNA processing, and subunit assembly with the aid of numerous assembly factors. Our previous study showed that the Arabidopsis thaliana protein arginine methyltransferase AtPRMT3 regulates pre-rRNA processing; however, the underlying molecular mechanism remains unknown. Here, we report that AtPRMT3 interacts with Ribosomal Protein S2 (RPS2), facilitating processing of the 90S/Small Subunit (SSU) processome and repressing nucleolar stress. We isolated an intragenic suppressor of atprmt3-2, which rescues the developmental defects of atprmt3-2 while produces a putative truncated AtPRMT3 protein bearing the entire N-terminus but lacking an intact enzymatic activity domain We further identified RPS2 as an interacting partner of AtPRMT3, and found that loss-of-function rps2a2b mutants were phenotypically reminiscent of atprmt3, showing pleiotropic developmental defects and aberrant pre-rRNA processing. RPS2B binds directly to pre-rRNAs in the nucleus, and such binding is enhanced in atprmt3-2. Consistently, multiple components of the 90S/SSU processome were more enriched by RPS2B in atprmt3-2, which accounts for early pre-rRNA processing defects and results in nucleolar stress. Collectively, our study uncovered a novel mechanism by which AtPRMT3 cooperates with RPS2B to facilitate the dynamic assembly/disassembly of the 90S/SSU processome during ribosome biogenesis and repress nucleolar stress.
核糖体生物发生主要发生在核仁中，涉及到前核糖体 RNA（pre-rRNA）和核糖体蛋白的协调表达、pre-rRNA 加工以及在众多组装因子的辅助下亚基的组装。我们之前的研究表明，拟南芥蛋白精氨酸甲基转移酶 AtPRMT3 调节 pre-rRNA 加工；然而，其潜在的分子机制尚不清楚。在这里，我们报告 AtPRMT3 与核糖体蛋白 S2（RPS2）相互作用，促进 90S/小亚基（SSU）加工体的加工，并抑制核仁应激。我们分离了一个 atprmt3-2 的基因内抑制子，该抑制子挽救了 atprmt3-2 的发育缺陷，同时产生了一种假定的截断 AtPRMT3 蛋白，该蛋白具有完整的 N 端但缺乏完整的酶活性结构域。我们进一步鉴定了 RPS2 是 AtPRMT3 的相互作用伙伴，并发现功能丧失 rps2a2b 突变体表现出与 atprmt3 相似的表型，表现出多种发育缺陷和异常的 pre-rRNA 加工。RPS2B 在核内直接结合 pre-rRNA，而这种结合在 atprmt3-2 中增强。一致地，90S/SSU 加工体的多个成分在 atprmt3-2 中被 RPS2B 更富集，这解释了早期 pre-rRNA 加工缺陷并导致核仁应激。总之，我们的研究揭示了一种新的机制，即 AtPRMT3 与 RPS2B 合作，促进核糖体生物发生过程中 90S/SSU 加工体的动态组装/拆卸，并抑制核仁应激。
