The assembly of ribosomal subunits starts in the nucleus, initiated by co-transcriptional folding of nascent ribosomal RNA (rRNA) transcripts and binding of ribosomal proteins and assembly factors. The internal transcribed spacer 2 (ITS2) is a precursor sequence to be processed from the intermediate 27S rRNA in the nucleoplasm; its removal is required for nuclear export of pre-60S particles. The proper processing of the ITS2 depends on multiple associated assembly factors and RNases. However, none of the structures of the known ITS2-binding factors is available. Here, we describe the modeling of the ITS2 subcomplex, including five assembly factors Cic1, Nop7, Nop15, Nop53, and Rlp7, using a combination of cryo-electron microscopy and cross-linking of proteins coupled with mass spectrometry approaches. The resulting atomic models provide structural insights into their function in ribosome assembly, and establish a framework for further dissection of their molecular roles in ITS2 processing. © 2016 The Protein Society.
Shan Wu, Dan Tan, John L Woolford, Meng-Qiu Dong, Ning Gao. Atomic modeling of the ITS2 ribosome assembly subcomplex from cryo-EM together with mass spectrometry-identified protein-protein crosslinks. Protein science : a publication of the Protein Society. 2017 Jan;26(1):103-112
PMID: 27643814
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