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Updated: May 14, 2026

A Reporter Based Cellular Assay for Monitoring Splicing Efficiency
Published on: September 15, 2021
Multiple tandem splicing silencer elements suppress aberrant splicing within the long exon 26 of the human
Umasuthan Srirangalingam1, Scott A Akker, Dennis Norman
1Department of Endocrinology, William Harvey Research Institute, Queen Mary University of London, John Vane Science Centre, Charterhouse Square, London EC1M 6BQ, UK.
Background:
Apolipoprotein B (APOB) is an integral component of the chylomicron and the atherogenic lipoproteins LDL and Lp(a). Exon 26 of the APOB pre-mRNA is unusually long at 7,572 nt and is constitutively spliced. It is also subject to RNA editing in the intestine, which generates a shortened isoform, APOB48, assembled exclusively into chylomicrons. Due to its length, exon 26 contains multiple pseudo splice sites which are not spliced, but which conform to the degenerate splice site consensus.
Results:
We demonstrate that these pseudo splice sites are repressed by multiple, tandem splicing silencers distributed along the length of exon 26. The distribution of these elements appears to be heterogeneous, with a greater frequency in the middle 4,800 nt of the exon.
Conclusion:
Repression of these splice sites is key to maintaining the integrity of exon 26 during RNA splicing and therefore the correct expression of both isoforms of APOB.
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