Distinct cytoplasmic maturation steps of 40S ribosomal subunit precursors require hRio2

J Cell Biol. 2009 Jun 29;185(7):1167-80. doi: 10.1083/jcb.200904048.

Abstract

During their biogenesis, 40S ribosomal subunit precursors are exported from the nucleus to the cytoplasm, where final maturation occurs. In this study, we show that the protein kinase human Rio2 (hRio2) is part of a late 40S preribosomal particle in human cells. Using a novel 40S biogenesis and export assay, we analyzed the contribution of hRio2 to late 40S maturation. Although hRio2 is not absolutely required for pre-40S export, deletion of its binding site for the export receptor CRM1 decelerated the kinetics of this process. Moreover, in the absence of hRio2, final cytoplasmic 40S maturation is blocked because the recycling of several trans-acting factors and cytoplasmic 18S-E precursor ribosomal RNA (rRNA [pre-rRNA]) processing are defective. Intriguingly, the physical presence of hRio2 but not its kinase activity is necessary for the release of hEnp1 from cytoplasmic 40S precursors. In contrast, hRio2 kinase activity is essential for the recycling of hDim2, hLtv1, and hNob1 as well as for 18S-E pre-rRNA processing. Thus, hRio2 is involved in late 40S maturation at several distinct steps.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Cell Cycle Proteins / genetics
  • Cell Cycle Proteins / metabolism
  • Cytoplasm / metabolism*
  • Genes, Reporter
  • HeLa Cells
  • Humans
  • Karyopherins / genetics
  • Karyopherins / metabolism
  • Molecular Sequence Data
  • Nuclear Proteins / genetics
  • Nuclear Proteins / metabolism*
  • Protein Precursors / genetics
  • Protein Precursors / metabolism*
  • Protein-Serine-Threonine Kinases / genetics
  • Protein-Serine-Threonine Kinases / metabolism*
  • RNA Interference
  • RNA Precursors / genetics
  • RNA Precursors / metabolism*
  • RNA-Binding Proteins / genetics
  • RNA-Binding Proteins / metabolism
  • Receptors, Cytoplasmic and Nuclear / genetics
  • Receptors, Cytoplasmic and Nuclear / metabolism
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • Ribosome Subunits, Small, Eukaryotic / genetics
  • Ribosome Subunits, Small, Eukaryotic / metabolism*
  • Sequence Alignment
  • Trans-Activators / genetics
  • Trans-Activators / metabolism
  • ran GTP-Binding Protein / genetics
  • ran GTP-Binding Protein / metabolism

Substances

  • Cell Cycle Proteins
  • Karyopherins
  • NOB1 protein, human
  • Nuclear Proteins
  • Protein Precursors
  • RNA Precursors
  • RNA-Binding Proteins
  • Receptors, Cytoplasmic and Nuclear
  • Recombinant Fusion Proteins
  • TXNL4B protein, human
  • Trans-Activators
  • exportin 1 protein
  • Protein-Serine-Threonine Kinases
  • RIOK2 protein, human
  • ran GTP-Binding Protein