The NF45/NF90 Heterodimer Contributes to the Biogenesis of 60S Ribosomal Subunits and Influences Nucleolar Morphology

Mol Cell Biol. 2015 Oct;35(20):3491-503. doi: 10.1128/MCB.00306-15. Epub 2015 Aug 3.


The interleukin enhancer binding factors ILF2 (NF45) and ILF3 (NF90/NF110) have been implicated in various cellular pathways, such as transcription, microRNA (miRNA) processing, DNA repair, and translation, in mammalian cells. Using tandem affinity purification, we identified human NF45 and NF90 as components of precursors to 60S (pre-60S) ribosomal subunits. NF45 and NF90 are enriched in nucleoli and cosediment with pre-60S ribosomal particles in density gradient analysis. We show that association of the NF45/NF90 heterodimer with pre-60S ribosomal particles requires the double-stranded RNA binding domains of NF90, while depletion of NF45 and NF90 by RNA interference leads to a defect in 60S biogenesis. Nucleoli of cells depleted of NF45 and NF90 have altered morphology and display a characteristic spherical shape. These effects are not due to impaired rRNA transcription or processing of the precursors to 28S rRNA. Consistent with a role of the NF45/NF90 heterodimer in nucleolar steps of 60S subunit biogenesis, downregulation of NF45 and NF90 leads to a p53 response, accompanied by induction of the cyclin-dependent kinase inhibitor p21/CIP1, which can be counteracted by depletion of RPL11. Together, these data indicate that NF45 and NF90 are novel higher-eukaryote-specific factors required for the maturation of 60S ribosomal subunits.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Nucleolus / metabolism
  • Cell Nucleus Shape
  • HEK293 Cells
  • HeLa Cells
  • Humans
  • Nuclear Factor 45 Protein / physiology*
  • Nuclear Factor 90 Proteins / physiology*
  • Protein Transport
  • Ribosomal Proteins / biosynthesis*
  • Ribosome Subunits, Large, Eukaryotic / metabolism


  • ILF2 protein, human
  • ILF3 protein, human
  • Nuclear Factor 45 Protein
  • Nuclear Factor 90 Proteins
  • Ribosomal Proteins