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Composition and three-dimensional EM structure of double affinity-purified, human prespliceosomal A complexes.

Little is known about the higher-order structure of prespliceosomal A complexes, in which pairing of the pre-mRNA's splice sites occurs. Here, human A complexes were isolated under physiological conditions by double-affinity selection. Purified complexes contained stoichiometric amounts of U1, U2 and pre-mRNA, and crosslinking studies indicated that these form concomitant base pairing interactions with one another. A complexes contained nearly all U1 and U2 proteins plus approximately 50 non-snRNP proteins. Unexpectedly, proteins of the hPrp19/CDC5 complex were also detected, even when A complexes were formed in the absence of U4/U6 snRNPs, demonstrating that they associate independent of the tri-snRNP. Double-affinity purification yielded structurally homogeneous A complexes as evidenced by electron microscopy, and allowed for the first time the generation of a three-dimensional structure. A complexes possess an asymmetric shape (approximately 260 x 200 x 195 angstroms) and contain a main body with various protruding elements, including a head-like domain and foot-like protrusions. Complexes isolated here are well suited for in vitro assembly studies to determine factor requirements for the A to B complex transition.

Pubmed ID: 17332742


  • Behzadnia N
  • Golas MM
  • Hartmuth K
  • Sander B
  • Kastner B
  • Deckert J
  • Dube P
  • Will CL
  • Urlaub H
  • Stark H
  • L├╝hrmann R


The EMBO journal

Publication Data

March 21, 2007

Associated Grants


Mesh Terms

  • Base Pairing
  • Humans
  • Immunoblotting
  • Immunoprecipitation
  • Mass Spectrometry
  • Microscopy, Electron
  • Models, Molecular
  • Oligonucleotides
  • Proteins
  • RNA Precursors
  • Spliceosomes
  • Tobramycin