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Molecular and Cellular Biology, May 2000, p. 3550-3557, Vol. 20, No. 10
Department of Veterinary Microbiology and
Preventive Medicine, Iowa State University, Ames, Iowa
50011,1 and Department of
Microbiology, University of Iowa, Iowa City, Iowa
522422
Received 15 October 1999/Returned for modification 30 November
1999/Accepted 22 February 2000
In addition to facilitating the nuclear export of incompletely
spliced viral mRNAs, equine infectious anemia virus (EIAV) Rev
regulates alternative splicing of the third exon of the
tat/rev mRNA. In the presence of Rev, this exon of the
bicistronic RNA is skipped in a fraction of the spliced mRNAs. In this
report, the cis-acting requirements for exon 3 usage were
correlated with sequences necessary for Rev binding and transport of
incompletely spliced RNA. The presence of a purine-rich exon splicing
enhancer (ESE) was required for exon 3 recognition, and the addition of Rev inhibited exon 3 splicing. Glutathione-S-transferase
(GST)-Rev bound to probes containing the ESE, and mutation of GAA
repeats to GCA within the ESE inhibited both exon 3 recognition in RNA splicing experiments and GST-Rev binding in vitro. These results suggest that Rev regulates alternative splicing by binding at or
near the ESE to block SR protein-ESE interactions. A 57-nucleotide sequence containing the ESE was sufficient to mediate Rev-dependent nuclear export of incompletely spliced RNAs. Rev export activity was
significantly inhibited by mutation of the ESE or by
trans-complementation with SF2/ASF. These results indicate
that the ESE functions as a Rev-responsive element and demonstrate that
EIAV Rev mediates exon 3 exclusion through protein-RNA interactions
required for efficient export of incompletely spliced viral RNAs.
0270-7306/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Binding of Equine Infectious Anemia Virus Rev to an Exon Splicing
Enhancer Mediates Alternative Splicing and Nuclear Export of
Viral mRNAs
*
Corresponding author. Mailing address: Dept. of VMPM,
Rm. 1136 Vet Med, Iowa State University, Ames, IA 50011. Phone: (515) 294-5158. Fax: (515) 294-8500. E-mail: scarp{at}iastate.edu.
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