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Journal of Cell Science, Vol 105, Issue 3 685-697, Copyright © 1993 by Company of Biologists
JOURNAL ARTICLES |
BJ Blencowe, M Carmo-Fonseca, SE Behrens, R Luhrmann and AI Lamond
European Molecular Biology Laboratory, Heidelberg, Germany.
An important goal of studies on pre-mRNA splicing is to identify factors that mediate the snRNP-snRNP and snRNP-pre-mRNA interactions that take place in the spliceosome. The U4/U6 snRNP is one of the four snRNPs that are subunits of spliceosomes. A rare patient autoimmune serum (MaS serum) has recently been identified that specifically immunoprecipitates U4/U6 snRNP from HeLa cell extracts through recognition of a 150 kDa autoantigen (p150) (Okano and Medsger, Journal of Immunology, 146, 535-542, 1991). Here we show that in addition to U4/U6 snRNP, p150 can also be detected associated with 20 S U5, U4/U6.U5 and 17 S U2 snRNPs, but not with U1 snRNP. In each particle p150 is present in sub-stoichiometric levels relative to the major snRNP proteins. We show that MaS serum selectively immunoprecipitates a sub-population of U4/U6 snRNPs in which the m3G-cap structure is masked and that p150 is preferentially associated with U6 snRNA in the U4/U6 particle. Anti-p150 antibodies show widespread nucleoplasmic staining, excluding nucleoli, with an elevated concentration in coiled bodies. This changes to a discrete punctate pattern when cells are treated with alpha-amanitin. Both the cytological and biochemical data indicate that the p150 autoantigen is a snRNP-associated factor in vivo. We also present biochemical evidence confirming that assembly of U4/U6 and U5 snRNPs into a U4/U6.U5 tri-snRNP particle is an integral step in the spliceosome assembly pathway. Addition of the purified U4/U6.U5 tri-snRNP restores splicing activity to inactivated HeLa nuclear extracts in which splicing had been inhibited by specific depletion of either the U4/U6 or U5 snRNPs.
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  D. Stanek, J. Pridalova-Hnilicova, I. Novotny, M. Huranova, M. Blazikova, X. Wen, A. K. Sapra, and K. M. Neugebauer Spliceosomal Small Nuclear Ribonucleoprotein Particles Repeatedly Cycle through Cajal Bodies Mol. Biol. Cell, June 1, 2008; 19(6): 2534 - 2543. [Abstract] [Full Text] [PDF]
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 C. G. Burns, R. Ohi, A. R. Krainer, and K. L. Gould Evidence that Myb-related CDC5 proteins are required for pre-mRNA splicing PNAS, November 23, 1999; 96(24): 13789 - 13794. [Abstract] [Full Text] [PDF]
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G. M. Molnar, A. Crozat, S.-K. Kraeft, Q. P. Dou, L. B. Chen, and A. B. Pardee Association of the mammalian helicase MAH with the pre-mRNA splicing complex PNAS, July 22, 1997; 94(15): 7831 - 7836. [Abstract] [Full Text] [PDF]
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