SMNrp is an essential pre-mRNA splicing factor required for the formation of the mature spliceosome

• Published in: The EMBO journal 2001-05, Vol.20 (9), p.2304-2314
• Main Authors: Meister, Gunter, Hannus, Stefan, Plöttner, Oliver, Baars, Tonie, Hartmann, Enno, Fakan, Stanislav, Laggerbauer, Bernhard, Fischer, Utz
• Format: Article
• Language: English
• Subjects: Animals; assembly; Cell Line; Cell Nucleus - metabolism; Cyclic AMP Response Element-Binding Protein; Humans; Mutation; Nerve Tissue Proteins - genetics; Nerve Tissue Proteins - metabolism; pre-mRNA splicing; Protein Binding - genetics; Protein Structure, Tertiary - physiology; Recombinant Proteins - genetics; Recombinant Proteins - metabolism; Ribonucleoprotein, U2 Small Nuclear - metabolism; Ribonucleoprotein, U4-U6 Small Nuclear - metabolism; Ribonucleoproteins, Small Nuclear - metabolism; RNA Precursors - metabolism; RNA Splicing - physiology; RNA Splicing Factors; RNA-Binding Proteins - metabolism; SMN Complex Proteins; SMNrp; SMNrp protein; snRNP U2 protein; snRNP U4 protein; snRNP U5 protein; snRNP U6 protein; SPF30; SPF30 protein; spliceosome; Spliceosomes - metabolism; Transcription, Genetic; U2 snRNP; Xenopus
• ISSN: 0261-4189; 1460-2075; 1460-2075
• DOI: 10.1093/emboj/20.9.2304

SMNrp, also termed SPF30, has recently been identified in spliceosomes assembled in vitro . We have functionally characterized this protein and show that it is an essential splicing factor. We show that SMNrp is a 17S U2 snRNP‐associated protein that appears in the pre‐spliceosome (complex A) and the mature spliceosome (complex B) during splicing. Immunodepletion of SMNrp from nuclear extract inhibits the first step of pre‐mRNA splicing by preventing the formation of complex B. Re‐addition of recombinant SMNrp to immunodepleted extract reconstitutes both spliceosome formation and splicing. Mutations in two domains of SMNrp, although similarly deleterious for splicing, differed in their consequences on U2 snRNP binding, suggesting that SMNrp may also engage in interactions with splicing factors other than the U2 snRNP. In agreement with this, we present evidence for an additional interaction between SMNrp and the [U4/U6·U5] tri‐snRNP. A candidate that may mediate this interaction, namely the U4/U6‐90 kDa protein, has been identified. We suggest that SMNrp, as a U2 snRNP‐associated protein, facilitates the recruitment of the [U4/U6·U5] tri‐snRNP to the pre‐spliceosome.