A comprehensive view on r- protein binding and rRNA domain structuring during early ribosome formation

ABSTRACT: Formation of the eukaryotic ribosomal subunits follows a strict regime to assemble ribosomal proteins (r-protein) with ribosomal RNAs (rRNA) while removing internal (ITS) and external (ETS) transcribed rRNA spacers. During early stages of large subunit (LSU) formation, ITS2 together with six assembly factors forms the characteristic foot structure of early nuclear pre-LSU particles. Here, we address the function of this foot structure during early stages of ribosome assembly. We present cryo-EM structures from wild-type cells and cells depleted for the foot structure factor Rlp7. We show that compaction of domain I of the 25S rRNA is strictly dependent on the presence of foot factors, while domain II folds independently. Furthermore, Rlp7-depletion accumulated small subunit (SSU) processome intermediates prior A1 cleavage and compaction of the individual domains of the 18S rRNA, providing also novel insights into the SSU-assembly process. SILAC labeling and affinity purification of co-transcriptional assembled pre-ribosomes enabled us to resolve the assembly line of the r-proteins step by step. This showed that incorporation of r-proteins in eukaryotes neither follows the bacterial regime nor a strict linear co-transcriptional mode. Instead, seed r-proteins might structurally define the individual rRNA domains before their compaction and fixation in the context of the SSU processome.

INSTRUMENT(S):

ORGANISM(S): Saccharomyces Cerevisiae (baker's Yeast)

SUBMITTER: Juliane Merl-Pham  

LAB HEAD: Helmut Bergler

PROVIDER: PXD058994 | Pride | 2026-02-02

REPOSITORIES: Pride