Prp8 impacts cryptic but not alternative splicing frequency

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• Pre-messenger RNA (pre-mRNA) splicing requires high fidelity to produce functional proteins.
• Aberrant splice site selection, including the use of cryptic splice sites, can lead to hereditary diseases due to nonfunctional proteins.
• Understanding how spliceosomes distinguish authentic from cryptic splice sites is crucial but poorly understood.

Purpose of the Study:

• To identify cellular factors influencing the frequency of cryptic splice site usage by the spliceosome.
• To investigate the role of the core spliceosome component Prp8 in regulating splice site selection.

Main Methods:

• A genetic screen in *Caenorhabditis elegans* was employed to identify factors affecting cryptic splice site usage.
• Two mutant alleles of the *prp-8* gene were identified.
• Complementary genetic and structural analyses were performed in yeast.
• High-throughput mRNA sequencing was used to analyze alternative splicing patterns in *prp-8* mutants.

Main Results:

• Two *prp-8* alleles were identified that alter cryptic splice site usage frequency.
• These alleles are implicated in the stability of the spliceosome's catalytic core.
• Despite altering cryptic splicing, overall alternative splicing patterns in *prp-8* mutant *C. elegans* remained largely unchanged.
• The findings suggest distinct mechanisms regulate cryptic versus alternative splicing.

Conclusions:

• The spliceosome possesses intrinsic mechanisms to minimize cryptic splice site utilization.
• These error-reduction mechanisms are evolutionarily conserved and operate independently of alternative splicing regulation.
• Prp8 plays a role in maintaining spliceosome fidelity by influencing catalytic core stability.