Splice-site pairing is an intrinsically high fidelity process

Area of Science:

• Molecular Biology
• Genetics
• Neuroscience

Background:

• Alternative splicing generates diverse mRNA isoforms in higher eukaryotes.
• A debate exists whether alternative splicing results from spliceosome inaccuracy or degenerate splice sites.
• Constitutively spliced pre-mRNAs provide a model to assess spliceosome accuracy.

Purpose of the Study:

• To quantitatively evaluate the accuracy of splice-site pairing by the spliceosome.
• To determine the frequency of incorrect exon-skipping events in constitutively spliced transcripts.
• To investigate the impact of spinal muscular atrophy on splicing fidelity.

Main Methods:

• Development of a quantitative assay to measure splice-site pairing accuracy.
• Analysis of exon-skipping events in pre-mRNA transcripts.
• Assessment of splicing fidelity in the context of reduced Survival of Motor Neuron (SMN) levels.

Main Results:

• The spliceosome exhibits a remarkably high accuracy in exon pairing.
• Pre-mRNA quality, potentially influenced by RNA polymerase II, may limit spliceosome accuracy.
• Reduced SMN levels, characteristic of spinal muscular atrophy, increase exon-pairing error rates.

Conclusions:

• All multi-intron genes are subject to alternative splicing.
• Reduced SMN causes a general splicing defect by altering splice-site pairing fidelity.
• Spliceosome accuracy is high, but can be compromised by factors like SMN deficiency.