Functional regions in the 5′ external transcribed spacer of yeast pre-rRNA
- Jing Chen1,2,3,
- Liman Zhang2 and
- Keqiong Ye3,4
- 1PTN Joint Graduate Program, School of Life Sciences, Tsinghua University, Beijing 100084, China
- 2National Institute of Biological Sciences, Beijing 102206, China
- 3Key Laboratory of RNA Biology, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
- 4University of Chinese Academy of Sciences, Beijing 100049, China
- Corresponding author: yekeqiong{at}ibp.ac.cn
Abstract
Ribosomal subunits are assembled on a precursor rRNA that includes four spacers in addition to mature rRNA sequences. The 5′ external transcribed spacer (5′ ETS) is the most prominent one that recruits U3 snoRNA and a plethora of proteins during the early assembly of 90S small subunit preribosomes. Here, we have conducted a comprehensive mutational analysis of 5′ ETS by monitoring the processing and assembly of a plasmid-expressed pre-18S RNA. Remarkably, nearly half of the 5′ ETS sequences, when depleted individually, are dispensable for 18S rRNA processing. The dispensable elements largely bind at the surface of the 90S structure. Defective assembly of 5′ ETS completely blocks the last stage of 90S formation yet has little effect on the early assembly of 5′ and central domains of 18S rRNA. Our study reveals the functional regions of 5′ ETS and provides new insight into the assembly hierarchy of 90S preribosomes.
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Article is online at http://www.rnajournal.org/cgi/doi/10.1261/rna.074807.120.
- Received January 9, 2020.
- Accepted March 21, 2020.
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