PNAS:植物可能使用朊病毒样的蛋白质形成记忆
2016年4月26日，国际著名学术期刊《美国国家科学院院刊》杂志在线发表了美国怀特黑德生物医学研究所的一项研究，研究提出朊病毒样的蛋白质可能构成了植物的一种记忆形式的基础。每年春天，植物根据诸如水合作用、温度和制造出了对遇到的冬季的记忆的春化作用等因素而开花。然而，人们对构成这类记忆的基础的分子机制的理解仍然不完备。由于已经发现朊病毒涉及了果蝇和海蛞蝓的神经元突触的维持，Susan Lindquist及其同事使用一种专门用于探测酵母的朊病毒样蛋白质域的算法，筛选了拟南芥的整套蛋白质的序列。这组作者识别出了474个候选蛋白质，把这项分析收窄到了3种涉及开花相关基因表达的蛋白质，然后使用在酵母中确立的方法测试了这些蛋白质的朊病毒样属性。在这些蛋白质中，Luminidependens (LD)满足了一种朊病毒的某些定义标准，即：维持一种低聚物自我复制状态的能力，可以在实验室实验中持续而可遗传地改变一种相关酵母蛋白质域的功能。此外，当移植到酵母朊病毒Sup35的时候，LD朊病毒域取代了这种酵母朊病毒域的功能，这提示LD可能是一种真正的朊病毒，而且很可能是首次来自植物的报告。这组作者说，植物区分冬季和非季节性寒潮的能力可能与诸如LD等蛋白质有关，这类蛋白质可能帮助触发或调控了与春化和开花有关的表观遗传学变化。
原文链接：
Luminidependens (LD) is an ArABIdopsis protein with prion behavior
原文摘要：
Prion proteins provide a unique mode of biochemical memory through self-perpetuating changes in protein conformation and function. They have been studied in fungi and mammals, but not yet identified in plants. Using a computational model, we identified candidate prion domains (PrDs) in nearly 500 plant proteins. Plant flowering is of particular interest with respect to biological memory, because its regulation involves remembering and integrating previously experienced environmental conditions. We investigated the prion-forming capacity of three prion candidates involved in flowering using a yeast model, where prion attributes are well defined and readily tested. In yeast, prions heritably change protein functions by templating monomers into higher-order assemblies. For most yeast prions, the capacity to convert into a prion resides in a distinct prion domain. Thus, new prion-forming domains can be identified by functional complementation of a known prion domain. The prion-like domains (PrDs) of all three of the tested proteins formed higher-order oligomers. Uniquely, the Luminidependens PrD (LDPrD) fully replaced the prion-domain functions of a well-characterized yeast prion, Sup35. Our results suggest that prion-like conformational switches are evolutionarily conserved and might function in a wide variety of normal biological processes.
作者：Sohini Chakrabortee
