Key Laboratory of RNA Science and Engineering, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.
University of Chinese Academy of Sciences, Beijing 100049, China.
Nucleic Acids Res. 2024 Sep 23;52(17):10630-10644. doi: 10.1093/nar/gkae606.
Ribosomal RNAs are processed in a complex pathway. We profiled rRNA processing intermediates in yeast at single-molecule and single-nucleotide levels with circularization, targeted amplification and deep sequencing (CircTA-seq), gaining significant mechanistic insights into rRNA processing and surveillance. The long form of the 5' end of 5.8S rRNA is converted to the short form and represents an intermediate of a unified processing pathway. The initial 3' end processing of 5.8S rRNA involves trimming by Rex1 and Rex2 and Trf4-mediated polyadenylation. The 3' end of 25S rRNA is formed by sequential digestion by four Rex proteins. Intermediates with an extended A1 site are generated during 5' degradation of aberrant 18S rRNA precursors. We determined precise polyadenylation profiles for pre-rRNAs and show that the degradation efficiency of polyadenylated 20S pre-rRNA critically depends on poly(A) lengths and degradation intermediates released from the exosome are often extensively re-polyadenylated.
核糖体 RNA 是通过一个复杂的途径进行加工的。我们利用环状化、靶向扩增和深度测序（CircTA-seq）技术，在单分子和单核苷酸水平上对酵母中的 rRNA 加工中间产物进行了分析，从而深入了解了 rRNA 的加工和监控机制。5.8S rRNA 5' 端的长链形式转化为短链形式，代表了统一加工途径的中间产物。5.8S rRNA 的初始 3' 端加工涉及 Rex1 和 Rex2 的修剪以及 Trf4 介导的多聚腺苷酸化。25S rRNA 的 3' 端由四个 Rex 蛋白的连续消化形成。在异常 18S rRNA 前体的 5' 降解过程中，会产生具有扩展 A1 位点的中间产物。我们确定了 pre-rRNA 的精确多聚腺苷酸化谱，并表明多聚腺苷酸化的 20S pre-rRNA 的降解效率取决于 poly(A) 长度，并且从 exosome 释放的降解中间产物通常会被广泛重新多聚腺苷酸化。
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