Analysis of the implication of the DBIRD complex (DBC1 and ZNF326/ZIRD) in gene expression and alternative splicing

Alternative mRNA splicing is the main reason vast mammalian proteomic complexity can be achieved with a limited number of genes. Splicing is physically and functionally coupled to transcription and the rate of transcript elongation has a profound effect on splicing. As the nascent pre-mRNA emerges from transcribing RNA polymerase II (RNAPII), it is assembled into a messenger ribonucleoprotein (mRNP) particle that represents its functional form, and the composition of which determines the fate of the mature transcript4. However, factors that connect the transcribing polymerase with the mRNP particle and help integrate transcript elongation with mRNA splicing remain obscure. Here, we characterized the interactome of chromatin-associated mRNP particles and thereby identified Deleted in Breast Cancer 1 (DBC1) and a protein we named ZIRD. These proteins are subunits of a novel protein complex, named DBIRD, which binds directly to RNAPII. DBIRD regulates alternative splicing of a large set of exons embedded in A/T-rich DNA, and is present at the affected exons. RNAi-mediated DBIRD depletion results in region-specific decreases in transcript elongation, particularly across areas encompassing affected exons. These data indicate that DBIRD complex acts at the interface between mRNP particles and RNAPII, integrating transcript elongation with regulation of alternative splicing.

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Close P, East P, Dirac-Svejstrup AB, Hartmann H, Heron M, Maslen S, Chariot A, Söding J, Skehel M, Svejstrup JQ