Mammalian nuclei contain foci which are highly enriched in components of the pre-mRNA splicing machinery

EMBO J. 1991 Jan;10(1):195-206.


The organization of the major snRNP particles in mammalian cell nuclei has been analysed by in situ labelling using snRNA-specific antisense probes made of 2'-OMe RNA. U3 snRNA is exclusively detected in the nucleolus while all the spliceosomal snRNAs are found in the nucleoplasm outside of nucleoli. Surprisingly, U2, U4, U5 and U6 snRNAs are predominantly observed in discrete nucleoplasmic foci. U1 snRNA is also present in foci but in addition is detected widely distributed throughout the nucleoplasm. An anti-peptide antibody specific for the non-snRNP splicing factor U2AF reveals it to have a similar distribution to U1 snRNA. Co-localization studies using confocal fluorescence microscopy prove that U2AF is present in the snRNA-containing foci. Antibody staining also shows the foci to contain snRNP-specific proteins and m3G-cap structures. The presence of major components of the nuclear splicing apparatus in foci suggests that these structures may play a role in pre-mRNA processing.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antisense Elements (Genetics)
  • Base Sequence
  • Cell Nucleus / metabolism
  • Cell Nucleus / ultrastructure*
  • Fluorescent Antibody Technique
  • HeLa Cells / cytology
  • HeLa Cells / metabolism
  • Humans
  • Molecular Sequence Data
  • Oligonucleotide Probes
  • RNA Precursors / genetics*
  • RNA Precursors / metabolism
  • RNA Splicing*
  • Ribonucleoproteins / metabolism
  • Ribonucleoproteins / ultrastructure
  • Ribonucleoproteins, Small Nuclear


  • Antisense Elements (Genetics)
  • Oligonucleotide Probes
  • RNA Precursors
  • Ribonucleoproteins
  • Ribonucleoproteins, Small Nuclear