PNAS:华南师大张钟徽教授等发表植物microRNA生物生成机制研究论文
近日，国际著名学术期刊《美国科学院院刊》在线发表了华南师范大学生命科学学院张钟徽教授和美国德克萨斯农工大学张秀仁研究组合作的题为“KETCH1 imports HYL1 to nucleus for miRNA biogenesis in Arabidopsis”的研究论文。论文揭示了拟南芥核转运蛋白KETCH1对miRNA剪切复合物亚基HYL1蛋白入核运输的调控机制。张钟徽教授、中国农大园艺学院博士生郭欣慰和德克萨斯农工大学生化系盖春晓硕士为论文的共同第一作者，张秀仁研究员为论文通讯作者。
microRNA(miRNA)是一类真核生物中广泛存在的内源非编码小分子RNA，它广泛地参与了动植物各种生物学过程的调控。植物miRNA主要在细胞核内通过由DCL1、HYL1和SE为核心蛋白元件组成的剪切复合物(microprocessor)剪切其前体pri-miRNA产生。目前，这些核心蛋白元件如何进入细胞核内完成功能，其具体调控过程尚未清楚。本研究以拟南芥HYL1过表达转基因植物为材料，通过免疫共沉淀方法分离HYL1复合物，鉴定出一个通过与HYL1蛋白互作参与miRNA生物合成途径的核转运蛋白KETCH1。拟南芥ketch1基因表达敲低突变体表现出典型miRNA生成途径突变体的表型，且miRNA积累水平显著降低。ketch1突变体中HYL1蛋白的核质分布有显著变化、核内HYL1蛋白显著减少，且pri-miRNA及pre-miRNA的积累增加。研究表明核转运蛋白KETCH1主要通过运输HYL1蛋白入核进而影响pri-miRNA在核内的剪切。
研究首次鉴定了参与miRNA剪切复合物核心元件入核运输的核转运蛋白，考虑到核转运蛋白及miRNA剪切复合物核心元件在动植物中的保守性，而该研究阐明机理在其他物种中尚未有报道，因此对揭示真核生物miRNA生物合成途径核心元件的核质运输过程有着重要意义。
原文链接：
KETCH1 imports HYL1 to nucleus for miRNA bioGENEsis inArabidopsis
原文摘要：
MicroRNA (miRNA) is processed from primary transcripts with hairpin structures (pri-miRNAs) by microprocessors in the nucleus. How cytoplasmic-borne microprocessor components are transported into the nucleus to fulfill their functions remains poorly understood. Here, we report KETCH1 (karyopherin enabling the transport of the cytoplasmic HYL1) as a partner of hyponastic leaves 1 (HYL1) protein, a core component of microprocessor in Arabidopsis and functional counterpart of DGCR8/Pasha in animals. Null mutation of ketch1 is embryonic-lethal, whereas knockdown mutation of ketch1 caused morphological defects, reminiscent of mutants in the miRNA pathway. ketch1 knockdown mutation also substantially reduced miRNA accumulation, but did not alter nuclear-cytoplasmic shuttling of miRNAs. Rather, the mutation significantly reduced nuclear portion of HYL1 protein and correspondingly compromised the pri-miRNA processing in the nucleus. We propose that KETCH1 transports HYL1 from the cytoplasm to the nucleus to constitute functional microprocessor in Arabidopsis. This study provides insight into the largely unknown nuclear-cytoplasmic trafficking process of miRNA biogenesis components through eukaryotes.
作者：张钟徽
