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Published July 15, 1993 | Published
Journal Article Open

The Saccharomyces cerevisiae PRP21 gene product is an integral component of the prespliceosome

Abstract

In Saccharomyces cerevisiae, the prp21 mutation causes accumulation of unspliced pre-mRNA at the nonpermissive temperature. We have cloned the PRP21 gene by complementation of its temperature-sensitive phenotype and found it to be the same as SPP91, an extragenic suppressor of the prp9 mutation previously studied in vivo by Chapon and Legrain [Chapon, C. & Legrain, P. (1992) EMBO J. 11, 3279-3288]. We have analyzed the effects of the prp21 mutation on splicing in vitro and have found that PRP21 is a splicing factor required for prespliceosome assembly. We also have analyzed the interaction of PRP21 with splicing complexes using anti-PRP21 antibodies and found that the RNA components of the prespliceosome--U1 and U2 small nuclear RNA (snRNA) particles and pre-mRNA--are specifically coimmunoprecipitated under splicing conditions in the presence of 0.2 M KCl. At higher KCl concentrations, U1 snRNP dissociates from splicing complexes; nevertheless, U2 snRNA and pre-mRNA are still efficiently immunoprecipitated. Immunoprecipitation of both U1 and U2 snRNA as well as pre-mRNA is ATP-dependent and requires a pre-mRNA capable of supporting prespliceosome assembly. Analysis of the unbound complexes in native gels confirmed that prespliceosomes are specifically immunoprecipitated by anti-PRP21 antibodies. These results demonstrate that PRP21 is an integral component of the prespliceosome and establishes a stable interaction with U2 snRNP and/or pre-mRNA in that complex.

Additional Information

© 1993 by the National Academy of Sciences. Contributed by John N. Abelson, April 16, 1993. We are grateful to Drs. M. Ares, Jr., P. Legrain, and S. Ruby, and to S. Fischer-Wells for communication of results prior to publication. We also thank the members of the Abelson laboratory for critical reading of the manuscript. This work was supported by National Institutes of Health Grant GM32637. The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.

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