A factor, U2AF, is required for U2 snRNP binding and splicing complex assembly

Cell. 1988 Jan 29;52(2):207-19. doi: 10.1016/0092-8674(88)90509-0.


Pre-mRNA splicing complex assembly is mediated by two specific pre-mRNA-snRNP interactions: U1 snRNP binds to the 5' splice site and U2 snRNP binds to the branch point. Here we show that unlike a purified U1 snRNP, which can bind to a 5' splice site, a partially purified U2 snRNP cannot interact with its target pre-mRNA sequence. We identify a previously uncharacterized activity, U2AF, that is required for the U2 snRNP-branch point interaction and splicing complex formation. Using RNA substrate exclusion and competition assays, we demonstrate that U2AF binds to the 3' splice site region prior to the U2 snRNP-branch point interaction. This provides an explanation for the necessity of the 3' splice site region in U2 snRNP binding and, hence, the first step of splicing.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Binding Sites
  • Carrier Proteins / isolation & purification
  • Carrier Proteins / metabolism
  • Centrifugation, Density Gradient
  • Chemical Fractionation
  • HeLa Cells
  • Heterogeneous-Nuclear Ribonucleoproteins
  • Humans
  • Immunosorbent Techniques
  • Micrococcal Nuclease / metabolism
  • Osmolar Concentration
  • Potassium Chloride
  • RNA Precursors / metabolism*
  • RNA Splicing*
  • RNA, Messenger / metabolism*
  • RNA-Binding Proteins
  • Ribonucleoproteins / isolation & purification
  • Ribonucleoproteins / metabolism*
  • Ribonucleoproteins, Small Nuclear


  • Carrier Proteins
  • Heterogeneous-Nuclear Ribonucleoproteins
  • RNA Precursors
  • RNA, Messenger
  • RNA-Binding Proteins
  • Ribonucleoproteins
  • Ribonucleoproteins, Small Nuclear
  • Potassium Chloride
  • Micrococcal Nuclease