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Molecular and Cellular Biology, November 1998, p. 6756-6766, Vol. 18, No. 11
Institut für Molekularbiologie und
Tumorforschung, Philipps-Universität Marburg, 35037 Marburg,
Germany
Received 4 May 1998/Returned for modification 16 June 1998/Accepted 12 August 1998
The human small nuclear ribonucleoprotein (snRNP) U5 is
biochemically the most complex of the snRNP particles, containing not only the Sm core proteins but also 10 particle-specific proteins. Several of these proteins have sequence motifs which suggest that they
participate in conformational changes of RNA and protein. Together, the
specific proteins comprise 85% of the mass of the U5 snRNP
particle. Therefore, protein-protein interactions should be
highly important for both the architecture and the function of this
particle. We investigated protein-protein interactions using both
native and recombinant U5-specific proteins. Native U5 proteins were
obtained by dissociation of U5 snRNP particles with the chaotropic
salt sodium thiocyanate. A stable, RNA-free complex containing the
116-kDa EF-2 homologue (116kD), the 200kD RNA unwindase, the 220kD
protein, which is the orthologue of the yeast Prp8p protein, and the
U5-40kD protein was detected by sedimentation analysis of the
dissociated proteins. By cDNA cloning, we show that the 40kD protein is
a novel WD-40 repeat protein and is thus likely to mediate regulated
protein-protein interactions. Additional biochemical analyses
demonstrated that the 220kD protein binds simultaneously to the 40- and
the 116kD proteins and probably also to the 200kD protein. Since the
220kD protein is also known to contact both the pre-mRNA and the U5
snRNA, it is in a position to relay the functional state of the
spliceosome to the other proteins in the complex and thus modulate
their activity.
0270-7306/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
The Human U5-220kD Protein (hPrp8) Forms a Stable RNA-Free
Complex with Several U5-Specific Proteins, Including an RNA Unwindase,
a Homologue of Ribosomal Elongation Factor EF-2, and a Novel
WD-40 Protein

and
*
Corresponding author. Mailing address: Institut
für Molekularbiologie und Tumorforschung,
Philipps-Universität Marburg, Emil Mannkopff-Str. 2, 35037 Marburg, Germany. Phone: (49) 6421 286240. Fax: (49) 6421 287008. E-mail: luehrmann{at}imt.uni-marburg.de.
Present address: Department of Molecular and Cell Biology,
University of California, Berkeley, CA 94720-3204.
Present address: ScheboTech GmbH, 35435 Wettenberg, Germany.
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