title: Structure of the pre-60S ribosomal subunit with nuclear export factor Arx1 bound at the exit tunnel.
abstract: Preribosomal particles evolve in the nucleus through transient interaction with biogenesis factors before export to the cytoplasm. Here, we report the architecture of the late pre-60S particle, purified from Saccharomyces cerevisiae, through Arx1, a nuclear export factor with structural homology to methionine aminopeptidases, or its binding partner Alb1. Cryo-EM reconstruction of the Arx1 particle at 11.9-Å resolution reveals regions of extra density on the pre-60S particle attributed to associated biogenesis factors, confirming the immature state of the nascent subunit. One of these densities could be unambiguously assigned to Arx1. Immunoelectron microscopy and UV cross-linking localize Arx1 close to the ribosomal exit tunnel, in direct contact with ES27, a highly dynamic eukaryotic rRNA expansion segment. The binding of Arx1 at the exit tunnel may position this export factor to prevent premature recruitment of ribosome-associated factors active during translation.
authors.affiliation: Biochemistry Center, Universität Heidelberg, Heidelberg, Germany.
authors.forename: Bettina
authors.initials: B
authors.lastname: Bradatsch
authors.forename: Christoph
authors.initials: C
authors.lastname: Leidig
authors.forename: Sander
authors.initials: S
authors.lastname: Granneman
authors.forename: Marén
authors.initials: M
authors.lastname: Gnädig
authors.forename: David
authors.initials: D
authors.lastname: Tollervey
authors.forename: Bettina
authors.initials: B
authors.lastname: Böttcher
authors.forename: Roland
authors.initials: R
authors.lastname: Beckmann
authors.forename: Ed
authors.initials: E
authors.lastname: Hurt
mesh_terms: D001692:Biological Transport; D002467:Cell Nucleus / Q000378:metabolism*; D020285:Cryoelectron Microscopy; D008958:Models, Molecular; D012270:Ribosomes; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000378:metabolism*
chemical_list: C546625:Arx1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins