Mol Cell Biol, April 1998, p. 1765-1773, Vol. 18, No. 4
Department of Molecular and Cell Biology,
University of California, Berkeley, California 94720-3204
Received 17 November 1997/Returned for modification 18 December
1997/Accepted 14 January 1998
The heterodimeric pre-mRNA splicing factor, U2AF (U2 snRNP
auxiliary factor), plays a critical role in 3' splice site selection. Although the U2AF subunits associate in a tight complex, biochemical experiments designed to address the requirement for both subunits in
splicing have yielded conflicting results. We have taken a genetic
approach to assess the requirement for the Drosophila U2AF
heterodimer in vivo. We developed a novel Escherichia coli copurification assay to map the domain on the Drosophila
U2AF large subunit (dU2AF50) that interacts with the
Drosophila small subunit (dU2AF38). A
28-amino-acid fragment on dU2AF50 that is both necessary
and sufficient for interaction with dU2AF38 was identified.
Using the copurification assay, we scanned this 28-amino-acid
interaction domain for mutations that abrogate heterodimer formation. A
collection of these dU2AF50 point mutants was then tested
in vivo for genetic complementation of a recessive lethal
dU2AF50 allele. A mutation that completely abolished
interaction with dU2AF38 was incapable of complementation,
whereas dU2AF50 mutations that did not effect heterodimer
formation rescued the recessive lethal dU2AF50 allele.
Analysis of heterodimer formation in embryo extracts derived from these
interaction mutant lines revealed a perfect correlation between the
efficiency of subunit association and the ability to complement the
dU2AF50 recessive lethal allele. These data indicate that
Drosophila U2AF heterodimer formation is essential for
viability in vivo, consistent with a requirement for both subunits in
splicing in vitro.
0270-7306/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Interaction between Subunits of Heterodimeric
Splicing Factor U2AF Is Essential In Vivo


*
Corresponding author. Mailing address: Department of
Molecular and Cell Biology, 401 Barker Hall #3204, University of
California, Berkeley, CA 94720-3204. Phone: (510) 642-1071. Fax: (510)
642-6062. E-mail: don_rio{at}UClink4.berkeley.edu.
Present address: Department of Molecular and Cellular Biology,
Harvard University, Cambridge, MA 02138.
Present address: Department of Cell Biology and Genetics, Erasmus
University, 3000 DR, Rotterdam, The Netherlands.
§
Present address: Oregon Health Science University, Portland, OR
97201.
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