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Characterization of novel SF3b and 17S U2 snRNP proteins, including a human Prp5p homologue and an SF3b DEAD‐box protein
Author(s) -
Will Cindy L.,
Urlaub Henning,
Achsel Tilmann,
Gentzel Marc,
Wilm Matthias,
Lührmann Reinhard
Publication year - 2002
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/cdf480
Subject(s) - planck , library science , biology , physics , computer science , quantum mechanics
Mass spectrometry was used to identify novel proteins associated with the human 17S U2 snRNP and one of its stable subunits, SF3b. Several additional proteins were identified, demonstrating that 17S U2 snRNPs are significantly more complex than previously thought. Two of the newly identified proteins, namely the DEAD‐box proteins SF3b125 and hPrp5 (a homologue of Saccharomyces cerevisiae Prp5p) were characterized further. Immunodepletion experiments with HeLa nuclear extract indicated that hPrp5p plays an important role in pre‐mRNA splicing, acting during or prior to prespliceosome assembly. The SF3b‐associated protein SF3b125 dissociates at the time of 17S U2 formation, raising the interesting possibility that it might facilitate the assembly of the 17S U2 snRNP. Finally, immunofluorescence/FISH studies revealed a differential subnuclear distribution of U2 snRNA, hPrp5p and SF3b125, which were enriched in Cajal bodies, versus SF3b155 and SF3a120, which were not; a model for 17S U2 snRNP assembly based on these findings is presented. Taken together, these studies provide new insight into the composition of the 17S U2 snRNP and the potential function of several of its proteins.