title: Architecture of the 90S Pre-ribosome: A Structural View on the Birth of the Eukaryotic Ribosome.
abstract: The 90S pre-ribosome is an early biogenesis intermediate formed during co-transcriptional ribosome formation, composed of ∼70 assembly factors and several small nucleolar RNAs (snoRNAs) that associate with nascent pre-rRNA. We report the cryo-EM structure of the Chaetomium thermophilum 90S pre-ribosome, revealing how a network of biogenesis factors including 19 β-propellers and large α-solenoid proteins engulfs the pre-rRNA. Within the 90S pre-ribosome, we identify the UTP-A, UTP-B, Mpp10-Imp3-Imp4, Bms1-Rcl1, and U3 snoRNP modules, which are organized around 5'-ETS and partially folded 18S rRNA. The U3 snoRNP is strategically positioned at the center of the 90S particle to perform its multiple tasks during pre-rRNA folding and processing. The architecture of the elusive 90S pre-ribosome gives unprecedented structural insight into the early steps of pre-rRNA maturation. Nascent rRNA that is co-transcriptionally folded and given a particular shape by encapsulation within a dedicated mold-like structure is reminiscent of how polypeptides use chaperone chambers for their protein folding.
authors.affiliation: Biochemie-Zentrum der Universität Heidelberg, 69120 Heidelberg, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Kornprobst
authors.affiliation: Gene Center, University of Munich, 81377 Munich, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Turk
authors.affiliation: Biochemie-Zentrum der Universität Heidelberg, 69120 Heidelberg, Germany.
authors.forename: Nikola
authors.initials: N
authors.lastname: Kellner
authors.affiliation: Gene Center, University of Munich, 81377 Munich, Germany.
authors.forename: Jingdong
authors.initials: J
authors.lastname: Cheng
authors.affiliation: Biochemie-Zentrum der Universität Heidelberg, 69120 Heidelberg, Germany.
authors.forename: Dirk
authors.initials: D
authors.lastname: Flemming
authors.affiliation: Biochemie-Zentrum der Universität Heidelberg, 69120 Heidelberg, Germany.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Koš-Braun
authors.affiliation: Biochemie-Zentrum der Universität Heidelberg, 69120 Heidelberg, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Koš
authors.affiliation: Biochemie-Zentrum der Universität Heidelberg, 69120 Heidelberg, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Thoms
authors.affiliation: Gene Center, University of Munich, 81377 Munich, Germany.
authors.forename: Otto
authors.initials: O
authors.lastname: Berninghausen
authors.affiliation: Gene Center, University of Munich, 81377 Munich, Germany. Electronic address: beckmann@genzentrum.lmu.de.
authors.forename: Roland
authors.initials: R
authors.lastname: Beckmann
authors.affiliation: Biochemie-Zentrum der Universität Heidelberg, 69120 Heidelberg, Germany. Electronic address: ed.hurt@bzh.uni-heidelberg.de.
authors.forename: Ed
authors.initials: E
authors.lastname: Hurt
mesh_terms: D002597:Chaetomium / Q000737:chemistry* / Q000145:classification; D020285:Cryoelectron Microscopy; D008958:Models, Molecular; D001678:Organelle Biogenesis; D012337:RNA, Ribosomal, 18S / Q000737:chemistry; D054683:Ribosome Subunits, Large, Eukaryotic / Q000737:chemistry; D054682:Ribosome Subunits, Small, Eukaryotic / Q000737:chemistry; D012270:Ribosomes / Q000737:chemistry* / Q000648:ultrastructure; D012441:Saccharomyces cerevisiae / Q000737:chemistry*
chemical_list: D012337:RNA, Ribosomal, 18S