CFIm25 regulates glutaminase alternative terminal exon definition to modulate miR-23 function

Area of Science:

• Molecular Biology
• Cancer Biology
• RNA Biology

Background:

• Alternative polyadenylation (APA) and alternative splicing (AS) are key post-transcriptional mechanisms that regulate gene expression.
• MicroRNAs (miRNAs) can repress gene expression by targeting 3' untranslated regions (3'UTRs) of mRNAs.
• Glutaminase (GLS) exists as two isoforms, KGA and GAC, with distinct 3'UTRs, and KGA is targeted by miR-23.

Purpose of the Study:

• To investigate the role of the APA regulator CFIm25 in controlling GLS mRNA isoforms (KGA and GAC).
• To elucidate the interplay between RNA processing (APA and AS) and miRNA repression in regulating GLS expression.
• To understand the impact of GLS isoform regulation on cancer cell apoptosis and metabolism.

Main Methods:

• Depletion of CFIm25 using knockdown techniques.
• Analysis of polyadenylation site usage and alternative splicing patterns of GLS mRNA.
• Assessment of miR-23 activity on different GLS 3'UTR lengths.
• Evaluation of apoptosis induction and rescue experiments.

Main Results:

• CFIm25 depletion induced a shift towards a proximal poly(A) site in the KGA 3'UTR and favored GAC 3'UTR exclusion.
• miR-23 effectively repressed the shortened KGA 3'UTR but had minimal impact on the full-length KGA 3'UTR.
• Down-regulation of the GAC isoform induced apoptosis, which was alleviated by reducing CFIm25 levels.

Conclusions:

• CFIm25 plays a critical role in regulating GLS mRNA isoform production through APA and AS.
• GLS expression is sensitive to RNA processing factor levels, indicating complex regulatory networks.
• The findings highlight the intricate relationship between RNA processing and miRNA activity in controlling glutamine metabolism in cancer.