Protein components specifically associated with prespliceosome and spliceosome complexes.
We have carried out a systematic analysis of the protein composition of highly purified mammalian spliceosomes. We show that > 30 distinct proteins, including 20 previously unidentified components [designated spliceosome-associated proteins (SAPs)], are specifically associated with the spliceosome in a salt-resistant complex. In contrast to these spliceosome-specific proteins, we show that hnRNP proteins are not tightly associated with purified prespliceosome and spliceosome complexes. The splicing factor U2AF65, U1 snRNP-specific proteins, and several SAPs are present in the earliest prespliceosome complex (E). A set of 10 proteins is then added to the first ATP-dependent prespliceosome complex (A), and concomitantly, a significant decrease in the level of U2AF65 is observed. The fully assembled spliceosome is formed by the addition of 12 proteins in a reaction that requires ATP and both the 5' and 3' splice sites.
Bennett
M
M
Department of Cellular and Molecular Physiology, Harvard Medical School, Boston, Massachusetts 02115.
Michaud
S
S
Kingston
J
J
Reed
R
R
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002846:Chromatography, Affinity; D015180:Electrophoresis, Gel, Two-Dimensional; D008322:Mammals; D010957:Plasmids; D011506:Proteins / Q000032:analysis*; D012322:RNA Precursors / Q000378:metabolism; D012326:RNA Splicing; D016601:RNA-Binding Proteins / Q000032:analysis; D012261:Ribonucleoproteins / Q000032:analysis; D017381:Spliceosomes / Q000737:chemistry*
D011506:Proteins; D012322:RNA Precursors; D016601:RNA-Binding Proteins; D012261:Ribonucleoproteins; D000255:Adenosine Triphosphate