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SMNrp is an essential pre‐mRNA splicing factor required for the formation of the mature spliceosome
Author(s) -
Meister Gunter,
Hannus Stefan,
Plöttner Oliver,
Baars Tonie,
Hartmann Enno,
Fakan Stanislav,
Laggerbauer Bernhard,
Fischer Utz
Publication year - 2001
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1093/emboj/20.9.2304
Subject(s) - biology , spliceosome , rna splicing , splicing factor , genetics , precursor mrna , polypyrimidine tract , computational biology , messenger rna , microbiology and biotechnology , rna , gene
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.