A complex immunodeficiency is based on U1 snRNP-mediated poly(A) site suppression

Area of Science:

• Molecular Biology
• Genetics
• Immunology

Background:

• Biallelic mutations in mRNA untranslated regions (UTRs) are rare causes of monogenetic diseases.
• The mechanisms underlying UTR-mediated genetic disorders are often poorly understood.
• A specific 3'UTR mutation was linked to a complex immunodeficiency syndrome due to reduced p14/robld3 mRNA levels.

Purpose of the Study:

• To elucidate the molecular mechanism by which a 3'UTR mutation leads to p14 mRNA suppression and immunodeficiency.
• To investigate the role of spliceosomal components in this novel disease mechanism.

Main Methods:

• Mutation analysis of the p14/robld3 3'UTR.
• Assessment of mRNA splicing and processing.
• Investigation of U1 small nuclear ribonucleoprotein (snRNP) interactions.
• Functional rescue experiments using histone processing signals.

Main Results:

• The 3'UTR mutation creates a functional 5' splice site (SS).
• Recognition of this aberrant SS by U1 snRNP leads to p14 mRNA suppression, independent of canonical splicing.
• Histone processing signals could rescue p14 expression, indicating interference with poly(A)-site 3' end processing.
• U1 snRNP appears to inhibit cleavage or poly(A) site recognition.

Conclusions:

• This is the first reported case of a 3'UTR mutation creating a functional 5'SS that causes a monogenetic disease.
• The findings highlight a novel mechanism of mRNA regulation and disease pathogenesis involving U1 snRNP.
• The study underscores the detrimental role of U1 snRNP in suppressing intronic poly(A) sites when it interferes with essential mRNA biogenesis.