The nuclear autoantigen La/SS-associated antigen B: one gene, three functional mRNAs

Area of Science:

• Molecular Biology
• Genetics
• Autoimmunity

Background:

• The nuclear autoantigen La (SS-A/Ro) is crucial in RNA processing and is implicated in autoimmune diseases like Sjogren syndrome.
• Understanding the transcriptional and translational regulation of the La gene is essential for elucidating its role in health and disease.

Purpose of the Study:

• To investigate the molecular mechanisms generating different messenger RNA (mRNA) forms of the nuclear autoantigen La.
• To determine the functionality of these distinct La mRNA variants in protein expression.

Main Methods:

• Analysis of gene transcription and alternative splicing pathways.
• Identification and characterization of novel exon structures (exon 1' and exon 1').
• Expression studies in transfected mouse cell lines to assess mRNA translation.

Main Results:

• Three distinct La mRNA forms were identified, arising from promoter switching and alternative splicing.
• Novel exon 1' and 1' structures were characterized, featuring GC-rich regions and oligo(U)-tails.
• All three La mRNA forms were expressed across various human and mouse tissues.
• Despite unusual upstream open reading frames, both exon 1' and 1' La mRNAs were successfully translated into functional nuclear La protein.

Conclusions:

• The La gene generates multiple functional mRNA transcripts through alternative splicing and promoter usage.
• The identified La mRNA variants are capable of producing the nuclear La protein, indicating their functional significance.
• These findings contribute to a deeper understanding of La gene regulation and its implications in autoimmune conditions.