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Published February 15, 1999 | Published
Journal Article Open

Control of 3′ splice site choice in vivo by ASF/SF2 and hnRNP A1

Abstract

The constitutive splicing factor ASF/SF2 has been shown to affect the choice between alternative splice sites by favoring the proximal as opposed to the distal choice. HnRNP A1 antagonizes ASF/SF2 by promoting the distal choice for competing 5′ splice sites. We have tested the in vivo effects of these proteins on alternative 3′ splice site choices. Cotransfection of a dihydrofolate reductase-calcitonin chimeric construct together with a plasmid specifying the SR protein ASF/SF2 into cells of several mammalian lines increased use of a proximal 3′ splice site, resulting in the inclusion of a terminal calcitonin exon. This stimulation of 3′ proximal splicing was antagonized by cotransfection with an hnRNP A1 plasmid. This effect of hnRNP A1 in promoting distal splicing was also seen in an hnRNP A1-deficient MEL cell line. A similar effect of hnRNP A1 was demonstrated with mutant hamster adenine phosphoribosyltransferase (aprt) transcripts that are normally constitutively spliced, suggesting that hnRNP A1 may be a general inhibitor of proximal splicing. Intron size also influenced splice site choice in mutant aprt transcripts, with larger introns favoring proximal splicing. These results support the idea that the ratios of particular but general splicing factors and hnRNPs play a role in alternative splicing.

Additional Information

© 1999 Oxford University Press. Received September 23, 1998. Accepted December 21, 1998. We are grateful to Bernard Chabot for providing us with DP27-17 and CB3C7 MEL cells, and to Gilbert Cote, James Manley and Adrian Krainer for providing the pF4-neo, ASF/SF2 and hnRNP A1 plasmids, respectively. We thank Bruce Brender and Ofra Kessler for the initial characterization of the splicing defect in CHO XA57 cells, and Mark Meuth for generously providing these cells. This work was supported by grant GM-22629 from the NIH.

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August 19, 2023
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