Structural snapshots of human pre-60S ribosomal particles before and after nuclear export

Abstract

Ribosome biogenesis is an elaborate and energetically expensive program that involve two hundred protein factors in eukaryotes. Nuclear export of pre-ribosomal particles is one central step which also serves as an internal structural checkpoint to ensure the proper completion of nuclear assembly events. Here we present four structures of human pre-60S particles isolated through a nuclear export factor NMD3, representing assembly stages immediately before and after nuclear export. These structures reveal locations of a dozen of human factors, including an uncharacterized factor TMA16 localized between the 5S RNA and the P0 stalk. Comparison of these structures shows a progressive maturation for the functional regions, such as peptidyl transferase centre and peptide exit tunnel, and illustrate a sequence of factor-assisted rRNA maturation events. These data facilitate our understanding of the global conservation of ribosome assembly in eukaryotes and species-specific features of human assembly factors.

RSL24D1 sustains steady-state ribosome biogenesis and pluripotency translational programs in embryonic stem cells

“…To further assess the degree of conservation between higher eukaryote RSL24D1 and its yeast homolog, we next compared the structure of mouse RSL24D1 with cryo-EM structures of yeast and human protein homologs, which have been recently obtained from nuclear pre-60S intermediates (Fig. 2A) (43-46). Similarly to yeast, cryo-EM structures of human pre-60S particles revealed the presence of RSL24D1 in nucleoplasmic stages of pre-60S assembly (states pre-A and A) while it was absent from later cytoplasmic stages of pre-60S maturation (46).…”

Revealing the host antiviral protein ZAP-S as an inhibitor of SARS-CoV-2 programmed ribosomal frameshifting

“…It is well established that ZAP can exert its antiviral activity by binding to CG-rich RNAs and thereby targeting them for degradation. Yet, ZAP does not bind to all CG-rich sequences and location of these sequences were shown to be crucial for ZAP interaction 36,37 . We speculate that, in addition to recognizing CG dinucleotides within the SARS-CoV-2 RNA frameshift site, ZAP-S also recognizes a particular fold within the putative pseudoknot.…”

Ribosomal Protein L10: From Function to Dysfunction

“…The incorporation of RPL10 in the large subunit is a late step in this maturation process and takes place in the cytoplasm. Recently, high-resolution structures of pre-60S intermediates at different assembly stages have been reported [34][35][36]. These intermediate structures, that represent the assembly steps immediately before and after nuclear export, helped to define the dynamic changes leading to and resulting from RPL10 incorporation [34][35][36].…”

“…Recently, high-resolution structures of pre-60S intermediates at different assembly stages have been reported [34][35][36]. These intermediate structures, that represent the assembly steps immediately before and after nuclear export, helped to define the dynamic changes leading to and resulting from RPL10 incorporation [34][35][36]. In the nucleus, immature large subunits lacking Rpl10 are complexed with the export adapter protein Nmd3 that recruits the nuclear export receptor Xpo1 (Crm1 in human) through a C-terminal nuclear export signal sequence and exports the pre-60S in the cytoplasm [34].…”