Improved identification of enriched peptide RNA cross-links from ribonucleoprotein particles (RNPs) by mass spectrometry

Nucleic Acids Res. 2007;35(15):e95. doi: 10.1093/nar/gkm540. Epub 2007 Jul 25.

Abstract

Direct UV cross-linking combined with mass spectrometry (MS) is a powerful tool to identify hitherto non-characterized protein-RNA contact sites in native ribonucleoprotein particles (RNPs) such as the spliceosome. Identification of contact sites after cross-linking is restricted by: (i) the relatively low cross-linking yield and (ii) the amount of starting material available for cross-linking studies. Therefore, the most critical step in such analyses is the extensive purification of the cross-linked peptide-RNA heteroconjugates from the excess of non-crosslinked material before MS analysis. Here, we describe a strategy that combines small-scale reversed-phase liquid chromatography (RP-HPLC) of UV-irradiated and hydrolyzed RNPs, immobilized metal-ion affinity chromatography (IMAC) to enrich cross-linked species and their analysis by matrix-assisted laser desorption/ionisation (MALDI) MS(/MS). In cases where no MS/MS analysis can be performed, treatment of the enriched fractions with alkaline phosphatase leads to unambiguous identification of the cross-linked species. We demonstrate the feasibility of this strategy by MS analysis of enriched peptide-RNA cross-links from UV-irradiated reconstituted [15.5K-61K-U4atac snRNA] snRNPs and native U1 snRNPs. Applying our approach to a partial complex of U2 snRNP allowed us to identify the contact site between the U2 snRNP-specific protein p14/SF3b14a and the branch-site interacting region (BSiR) of U2 snRNA.

Publication types

  • Research Support, Non-U.S. Gov't
  • Validation Study

MeSH terms

  • Alkaline Phosphatase
  • Amino Acid Sequence
  • Binding Sites
  • Chromatography, Affinity
  • Chromatography, Liquid / methods
  • Computational Biology
  • Molecular Sequence Data
  • Peptides / chemistry*
  • Peptides / isolation & purification
  • RNA, Small Nuclear / chemistry*
  • RNA, Small Nuclear / isolation & purification
  • Ribonucleoprotein, U1 Small Nuclear / chemistry
  • Ribonucleoprotein, U1 Small Nuclear / radiation effects
  • Ribonucleoprotein, U2 Small Nuclear / chemistry
  • Ribonucleoprotein, U2 Small Nuclear / radiation effects
  • Ribonucleoproteins, Small Nuclear / chemistry*
  • Ribonucleoproteins, Small Nuclear / radiation effects
  • Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization*
  • Ultraviolet Rays

Substances

  • Peptides
  • RNA, Small Nuclear
  • Ribonucleoprotein, U1 Small Nuclear
  • Ribonucleoprotein, U2 Small Nuclear
  • Ribonucleoproteins, Small Nuclear
  • Alkaline Phosphatase