U1-mediated exon definition interactions between AT-AC and GT-AG introns.
A minor class of metazoan introns has well-conserved splice sites with 5'-AU-AC-3' boundaries, compared to the 5'-GU-AG-3' boundaries and degenerate splice sites of conventional introns. Splicing of the AT-AC intron 2 of a sodium channel (SCN4A) precursor messenger RNA in vitro did not require inhibition of conventional splicing and required adenosine triphosphate, magnesium, and U12 small nuclear RNA (snRNA). When exon 3 was followed by the 5' splice site from the downstream conventional intron, splicing of intron 2 was greatly stimulated. This effect was U1 snRNA-dependent, unlike the basal AT-AC splicing reaction. Therefore, U1-mediated exon definition interactions can coordinate the activities of major and minor spliceosomes.
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Cold Spring Harbor Laboratory, Post Office Box 100, Cold Spring Harbor, NY 11724-2208, USA. krainer@cshl.org
Krainer
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D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D005091:Exons; D006367:HeLa Cells; D006801:Humans; D007438:Introns; D008274:Magnesium / Q000494:pharmacology; D012326:RNA Splicing; D012342:RNA, Small Nuclear / Q000378:metabolism*; D017412:Ribonucleoprotein, U1 Small Nuclear / Q000378:metabolism; D017411:Ribonucleoproteins, Small Nuclear / Q000378:metabolism; D015222:Sodium Channels / Q000235:genetics*; D017381:Spliceosomes / Q000235:genetics
D012342:RNA, Small Nuclear; D017412:Ribonucleoprotein, U1 Small Nuclear; D017411:Ribonucleoproteins, Small Nuclear; D015222:Sodium Channels; C096986:U12 small nuclear RNA; D000255:Adenosine Triphosphate; D008274:Magnesium