研究人员报道了成熟的人类小亚基（SSU）加工体的高分辨率冷冻电镜结构，分辨率为2.7至3.9埃。这些结构揭示了在SSU加工体成熟过程中实现关键进展的分子机制。这些颗粒内的RNA折叠状态被传达给关键的酶并与之协调，这些酶驱动着不可逆转的步骤，例如有针对性的外显子介导的RNA降解、蛋白质引导的特异性核酸内切，以及严格控制的RNA解绕。
这些保守的机制突出了SSU加工体惊人的结构可塑性，并赋予了这个4.5兆道尔顿的核仁组装体从内部成熟小核糖体亚单位的独特能力。
据介绍，人类小亚基加工体通过将RNA折叠与随后的RNA切割和加工步骤相联系来介导小核糖体亚基的早期成熟。
附：英文原文
Title: Nucleolar maturation of the human small subunit processome
Author: Sameer Singh, Arnaud Vanden Broeck, Linamarie Miller, Malik Chaker-Margot, Sebastian Klinge
Issue&Volume: 2021-09-10
Abstract: The human small subunit processome mediates early maturation of the small ribosomal subunit by coupling RNA folding to subsequent RNA cleavage and processing steps. We report the high-resolution cryo–electron microscopy structures of maturing human small subunit (SSU) processomes at resolutions of 2.7 to 3.9 angstroms. These structures reveal the molecular mechanisms that enable crucial progressions during SSU processome maturation. RNA folding states within these particles are communicated to and coordinated with key enzymes that drive irreversible steps such as targeted exosome-mediated RNA degradation, protein-guided site-specific endonucleolytic RNA cleavage, and tightly controlled RNA unwinding. These conserved mechanisms highlight the SSU processome’s impressive structural plasticity, which endows this 4.5-megadalton nucleolar assembly with the distinctive ability to mature the small ribosomal subunit from within.
DOI: abj5338
Source: https://www.science.org/doi/10.1126/science.abj5338