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ID: 17049.0, MPI für biophysikalische Chemie / Zelluläre Biochemie (Prof. Reinhard Lührmann)
Human U4/U6.U5 and U4atac/U6atac.U5 tri-snRNPs exhibit similar protein compositions
Authors:Schneider, C.; Will, C. L.; Makarova, O.; Makarov, E. M.; Luehrmann, R.
Date of Publication (YYYY-MM-DD):2002-05
Title of Journal:Molecular and Cellular Biology
Issue / Number:10
Start Page:3219
End Page:3229
Review Status:Peer-review
Audience:Not Specified
Abstract / Description:In the U12-dependent spliceosome, the U4atac/U6atac snRNP represents the functional analogue of the major U4/U6 snRNP. Little information is available presently regarding the protein composition of the former snRNP and its association with other snRNPs. In this report we show that human U4atac/U6atac di- snRNPs associate with U5 snRNPs to form a 25S U4atac/U6atac.U5 trimeric particle. Comparative analysis of minor and major tri- snRNPs by using immunoprecipitation experiments revealed that their protein compositions are very similar, if not identical. Not only U5-specific proteins but, surprisingly, all tested U4/U6- and major tri-snRNP-specific proteins were detected in the minor tri-snRNP complex. Significantly, the major tri- snRNP-specific proteins 65K and 110K, which are required for integration of the major tri-snRNP into the U2-dependent spliceosome, were among those proteins detected in the minor tri-snRNP, raising an interesting question as to how the specificity of addition of tri-snRNP to the corresponding spliceosome is maintained. Moreover, immunodepletion studies demonstrated that the U4/U6-specific 61K protein, which is involved in the formation of major tri-snRNPs, is essential for the association of the U4atac/U6atac di-snRNP with U5 to form the U4atac/U6atac.U5 tri-snRNP. Subsequent immunoprecipitation studies demonstrated that those proteins detected in the minor tri-snRNP complex are also incorporated into U12-dependent spliceosomes. This remarkable conservation of polypeptides between minor and major spliceosomes, coupled with the absence of significant sequence similarity between the functionally analogous snRNAs, supports an evolutionary model in which most major and minor spliceosomal proteins, but not snRNAs, are derived from a common ancestor.
Comment of the Author/Creator:Date: 2002, MAY
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für biophysikalische Chemie/Abt. Reinhard Lührmann / 100
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