Building Knowledge About Alternatively-spliced Dual-Coding Exons

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Abstract Most protein-coding genes in humans and other eukaryotes are made up of a collection of exons, which are concatenated to form the messenger RNA (mRNA) that encodes a final protein product. The well-known phenomenon of alternative splicing makes it possible for a single gene to encode multiple protein products, by conditionally including only a subset of the gene’s exons into the expressed mRNA. A more surprising mechanism for producing alternate protein products is to utilize an alternate reading frame of a standard exon, through aberrant splicing; using custom software built in our research group, we have found that this mechanism appears to be quite common. Specifically, ~13% of all human genes include at least one exon that conditionally encodes alternate peptides, and these “dual-coding exons” are highly-conserved: 98% correspond to homologous exons in the mouse genome that also encode two open reading frames. Light exploration has identified dozens of human genes that show tissue-specific patterns of reading frame usage, suggesting a functional role for at least some of these variants. Here, we describe a plan to (i) leverage massive public atlases of human tissue-specific and development-specific RNA-Seq and mass spectrometry data to tabulate the extent of differential use of these frame-shifted splicing variants, and to (ii) analyze the computationally-predicted structural and functional impact of dual-coding variants, and the sequence signals controlling them. The results of these analyses will be accumulated for release in an open and accessible web service.