An element in the 5' common exon of the NCAM alternative splicing unit interacts with SR proteins and modulates 5' splice site selection.

AUTOR(ES)

Côté, J

RESUMO

The neural cell adhesion molecule (NCAM) gene contains an 801 nt exon that is included preferentially in neuronal cells. We have set up an in vitro splicing system that mimics the neuro-specific alternative splicing profile of NCAM exon 18. Splicing regulation is observed using model pre-mRNAs that contain competing 5' or 3' splice sites, suggesting that distinct pathways regulate NCAM 5' and 3' splice site selection. While inclusion of exon 18 is the predom-inant choice in neuronal cells, an element in the 5' common exon 17 improves exon 17/exon 19 splicing in a neuronal cell line. A similar behavior is observed in vitro as the element can stimulate the 5' splice site of exon 17 or a heterologous 5' splice site. The minimal 32 nt sequence of the exon 17 enhancer consists of purine stretches and A/C motifs. Mutations in the purine stretches compromise the binding of SR proteins and decreases splicing stimulation in vitro. Mutations in the A/C motifs do not affect SR protein binding but reduce enhancing activity. Our results suggest that the assembly of an enhancer complex containing SR proteins in a 5' common exon ensures that NCAM mRNAs lacking exon 18 are made in neuronal cells.

Documentos Relacionados

• General splicing factors SF2 and SC35 have equivalent activities in vitro, and both affect alternative 5' and 3' splice site selection.
• Accurate selection of a 5' splice site requires sequences within fibronectin alternative exon B.
• Alternative 5' splice site selection induced by heat shock.
• An intron element modulating 5' splice site selection in the hnRNP A1 pre-mRNA interacts with hnRNP A1.
• Identification of a Bidirectional Splicing Enhancer: Differential Involvement of SR Proteins in 5′ or 3′ Splice Site Activation