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Molecular and Cellular Biology, December 1998, p. 6910-6920, Vol. 18, No. 12
Department of Biochemistry, University of
Cambridge, Cambridge CB2 1GA, United Kingdom
Received 13 July 1998/Returned for modification 6 August
1998/Accepted 9 September 1998
Assembly of spliceosomes involves a number of sequential steps in
which small nuclear ribonucleoprotein particles (snRNPs) and some
non-snRNP proteins recognize the splice site sequences and undergo
various conformational rearrangements. A number of important
intermolecular RNA-RNA duplexes are formed transiently during the
process of splice site recognition. Various steps in the assembly
pathway are dependent upon ATP hydrolysis, either for protein
phosphorylation or for the activity of helicases, which may modulate
the RNA structures. Major efforts have been made to identify proteins
that interact with specific regions of the pre-mRNA during the stages
of spliceosome assembly and catalysis by site-specific UV
cross-linking. However, UV cross-linking is often inefficient for the
detection of proteins that interact with base-paired RNA. Here we have
used the complementary approach of methylene blue-mediated
photo-cross-linking to detect specifically proteins that interact with
the duplexes formed between pre-mRNA and small nuclear RNA (snRNA). We
have detected a novel cross-link between a 65-kDa protein (p65) and the
5' splice site. A range of data suggest that p65 cross-links to the
transient duplex formed by U1 snRNA and the 5' splice site. Moreover,
although p65 cross-linking requires only a 5' splice site within the
pre-mRNA, it also requires ATP hydrolysis, suggesting that its
detection reflects a very early ATP-dependent event during splicing.
0270-7306/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Detection of a Novel ATP-Dependent Cross-Linked Protein at
the 5' Splice Site-U1 Small Nuclear RNA Duplex by Methylene
Blue-Mediated Photo-Cross-Linking

and
*
Corresponding author. Mailing address: Department of
Biochemistry, 80, Tennis Court Rd., Old Addenbrookes Site, University of Cambridge, Cambridge CB2 1GA, United Kingdom. Phone: 44-1223-333655 or 333665. Fax: 44-1223-766002. E-mail:
cwjs1{at}mole.bio.cam.ac.uk.
Present address: Molecular Cancer Biology, Duke University Medical
Center, Durham, NC 27710.
Present address: Centre de Genetique Moleculaire-CNRS,
Gif-sur-Yvette, Cedex, France.
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