ELAV/Hu RNA binding proteins determine multiple programs of neural alternative splicing

Area of Science:

• Molecular Biology
• Neuroscience
• Genetics

Background:

• ELAV/Hu factors are conserved RNA binding proteins (RBPs) crucial for mRNA processing and regulation.
• While Drosophila Elav's neural role is known, its broader transcriptome impact and paralog interactions remain unclear.
• Previous work linked ELAV/Hu factors to neural-specific lengthened 3' UTR isoforms.

Purpose of the Study:

• To investigate the impact of ELAV/Hu factors on mRNA splicing.
• To explore functional overlap among Drosophila ELAV/Hu paralogs (Elav, Fne, Rbp9).
• To elucidate the mechanistic link between 3' UTR extension and alternative last exon (ALE) splicing.

Main Methods:

• Ectopic expression of Elav, Fne, and Rbp9 in Drosophila to assess splicing changes.
• Analysis of double mutants (elav/fne) in the larval central nervous system (CNS).
• Identification of ELAV/Hu motifs in introns flanking regulated exons.
• ELAV/Hu motif analysis in relation to polyadenylation signals.
• RNA binding protein immunoprecipitation (CLIP) data analysis (Elav-CLIP).

Main Results:

• Ectopic expression of each ELAV/Hu factor altered hundreds of cassette exon and ALE splicing choices.
• Double mutants (elav/fne) showed opposing effects on splicing compared to single mutants.
• ELAV/Hu motifs were enriched in introns of exons suppressed by these factors.
• ELAV/Hu factors globally promote distal ALE splicing, linked to 3' UTR extensions via polyadenylation signal bypass.
• Conservation of these mechanisms was observed in mammalian neurons.

Conclusions:

• ELAV/Hu RBPs orchestrate diverse mRNA processing programs, including splicing and 3' UTR diversification.
• These factors play conserved roles in neuronal gene expression regulation across species.
• ELAV/Hu factors are key regulators of neuronal isoform complexity.