Are vertebrate exons scanned during splice-site selection?

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• The scanning mechanism is a model for vertebrate splicing coordination.
• Previous models predicted intron polarity, but evidence is lacking.
• An alternative hypothesis suggests exons, not introns, are the unit of recognition.

Purpose of the Study:

• To investigate the exon scanning mechanism for splice site selection.
• To determine if 5' splice site recognition within 3'-terminal exons affects polyadenylation.
• To explore the interaction between splicing and polyadenylation factors.

Main Methods:

• In vitro and in vivo assays to detect splice site recognition.
• Measurement of polyadenylation rates.
• Ultraviolet crosslinking to assess polyadenylation factor binding.

Main Results:

• A 5' splice site within a 3'-terminal exon was recognized both in vitro and in vivo.
• This recognition led to a decrease in polyadenylation rates.
• Ultraviolet crosslinking of a polyadenylation factor was reduced when splice sites were within 300 nucleotides.

Conclusions:

• The findings support an exon scanning mechanism for splice site selection in vertebrates.
• Splicing and polyadenylation factors interact during 3'-terminal exon recognition.
• The proximity of 5' and 3' splice sites influences these interactions.