The cellular EJC interactome reveals higher-order mRNP structure and an EJC-SR protein nexus
Department of Biochemistry and Molecular Pharmacology; Program in Bioinformatics and Integrative Biology
*Exons; Humans; Multiprotein Complexes; Proteome; RNA Precursors; *RNA Processing, Post-Transcriptional; RNA Splicing; Ribonucleoproteins
Biochemistry, Biophysics, and Structural Biology | Bioinformatics | Computational Biology | Genetics and Genomics
In addition to sculpting eukaryotic transcripts by removing introns, pre-mRNA splicing greatly impacts protein composition of the emerging mRNP. The exon junction complex (EJC), deposited upstream of exon-exon junctions after splicing, is a major constituent of spliced mRNPs. Here, we report comprehensive analysis of the endogenous human EJC protein and RNA interactomes. We confirm that the major "canonical" EJC occupancy site in vivo lies 24 nucleotides upstream of exon junctions and that the majority of exon junctions carry an EJC. Unexpectedly, we find that endogenous EJCs multimerize with one another and with numerous SR proteins to form megadalton sized complexes in which SR proteins are super-stoichiometric to EJC core factors. This tight physical association may explain known functional parallels between EJCs and SR proteins. Further, their protection of long mRNA stretches from nuclease digestion suggests that endogenous EJCs and SR proteins cooperate to promote mRNA packaging and compaction.
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Citation: Cell. 2012 Nov 9;151(4):750-64. doi: 10.1016/j.cell.2012.10.007. Link to article on publisher's site
Singh, Guramrit; Kucukural, Alper; Cenik, Can; Leszyk, John D.; Shaffer, Scott A.; Weng, Zhiping; and Moore, Melissa J., "The cellular EJC interactome reveals higher-order mRNP structure and an EJC-SR protein nexus" (2012). Program in Bioinformatics and Integrative Biology Publications and Presentations. 7.