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In vitro studies of the Prp9.Prp11.Prp21 complex indicate a pathway for U2 small nuclear ribonucleoprotein activation.

Authors
  • Wiest, D K
  • O'Day, C L
  • Abelson, J
Type
Published Article
Journal
Journal of Biological Chemistry
Publisher
American Society for Biochemistry & Molecular Biology (ASBMB)
Publication Date
Dec 27, 1996
Volume
271
Issue
52
Pages
33268–33276
Identifiers
PMID: 8969185
Source
Medline
License
Unknown

Abstract

Pre-mRNA splicing takes place on a large ribonucleoprotein particle, the spliceosome which contains the five small nuclear ribonucleoproteins (snRNPs), U1, U2, U4, U5, and U6. In Saccharomyces cerevisiae the mRNA splicing factors, Prp9, Prp11, and Prp21, are necessary for addition of the U2 snRNP to the pre-mRNA in an early step of spliceosome assembly. This paper describes a study of interactions between these proteins and their role in spliceosome assembly. The proteins were expressed in Escherichia coli. Prp9 and Prp11 were purified by metal affinity chromatography. Prp21 was purified using a solubilization/renaturation protocol. We have combined these separately purified proteins and present direct evidence of a Prp9.Prp11.Prp21 protein complex that is functional in in vitro splicing assays. Characteristics of this Prp9.Prp11.Prp21 complex were further investigated using proteins synthesized in vitro. In addition, we found that Prp9, Prp11, and Prp21 influence the structure of the U2 snRNP in a manner that alters the accessibility of the branch point pairing region of the U2 snRNA to oligonucleotide- directed RNaseH cleavage. We present a model, based on the data presented here and in the accompanying paper, for a combined role of Prp9, Prp11, Prp21, and Prp5 in activating the U2 snRNP for assembly into the pre-spliceosome.

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