The fourth exon of the mouse polymeric immuno-globulin receptor (pIgR) is 654 nt long and, despite being surrounded by large introns, is constitutively spliced into the mRNA. Deletion of an 84 nt sequence from this exon strongly activated both cryptic 5' and 3' splice sites surrounding a 78 nt cryptic intron. The 84 nt deletion is just upstream of the cryptic 3' splice site; the cryptic 3' spli...

Alternative pre-mRNA splicing may be the most efficient and widespread mechanism to generate multiple protein isoforms from single genes. Here, we describe the genomic analysis of one of the most frequent types of alternative pre-mRNA splicing, alternative 5'- and 3'-splice-site selection. Using an EST-based alternative splicing database recording >47,000 alternative splicing events, we determi...

The adenovirus late region 1 (L1) represents an example of an alternatively spliced gene where one 5' splice site is spliced to two alternative 3' splice sites, to produce two mRNAs; the 52,55K and IIIa mRNAs, respectively. Accumulation of the L1 mRNAs is temporally regulated during the infectious cycle. Thus, the proximal 3' splice site (52,55K mRNA) is used at all times during the infectious ...

The interactions established at the 5'-splice site during spliceosome assembly are likely to be important for both precise recognition of the upstream intron boundary and for positioning this site in the active center of the spliceosome. Definition of the RNA-RNA and the RNA-protein interactions at the 5' splice site would be facilitated by the use of a small substrate amenable to modification ...

Pre-mRNA transcripts in a variety of organisms, including plants, Drosophila and Caenorhabditis elegans, contain introns which are significantly richer in adenosine and uridine residues than their flanking exons. Previous analyses using exonic and intronic replacements between two nonequivalent 5'splice sites in the 469 nt long rbcS3A intron 1 provided the first evidence indicating that, in bot...

Pre-mRNA splicing is carried out by the spliceosome, which identifies exons and removes intervening introns. In vertebrates, most splice sites are initially recognized by the spliceosome across the exon, because most exons are small and surrounded by large introns. This gene architecture predicts that efficient exon recognition depends largely on the strength of the flanking 3' and 5' splice si...

Purine-rich enhancers are exon sequences that promote inclusion of alternative exons, usually via activation of weak upstream 3' splice sites. A recently described purine-rich enhancer from the caldesmon gene has an additional activity by which it directs selection of competing 5' splice sites within an alternative exon. In this study, we have compared the caldesmon enhancer with another purine...

Splice site selection is a key element of pre-mRNA splicing. Although it is known to involve specific recognition of short consensus sequences by the splicing machinery, the mechanisms by which 5' splice sites are accurately identified remain controversial and incompletely resolved. The human F7 gene contains in its seventh intron (IVS7) a 37-bp VNTR minisatellite whose first element spans the ...