The RNA splicing factor hSlu7 is required for correct 3' splice-site choice

Area of Science:

• Molecular Biology
• RNA Splicing Mechanisms

Background:

• Messenger RNA (mRNA) splicing involves two catalytic steps to produce mature mRNA.
• Step II of splicing requires exon 1 to attack an adenine-guanine (AG) dinucleotide at the 3' splice site.
• The selection of the correct AG dinucleotide from multiple downstream options is not fully understood.

Purpose of the Study:

• To identify and characterize a metazoan splicing factor responsible for correct AG dinucleotide selection.
• To elucidate the mechanism by which the correct AG is distinguished during splicing.

Main Methods:

• Analysis of spliceosomes assembled in the absence of the identified splicing factor (hSlu7).
• Investigating the fidelity of AG selection in vitro.

Main Results:

• A metazoan splicing factor, hSlu7, was identified as essential for correct AG selection.
• In the absence of hSlu7, the use of the correct AG is suppressed, and incorrect AGs are activated.
• Exon 1 is loosely associated with spliceosomes lacking hSlu7, preventing precise targeting of the correct AG.

Conclusions:

• hSlu7 is crucial for maintaining fidelity in mRNA splicing by ensuring the correct AG dinucleotide is targeted.
• The protein hSlu7 functions by tightly holding exon 1 within the spliceosome, facilitating accurate attack on the prespecified AG.