The RNA processing factors THRAP3 and BCLAF1 promote the DNA damage response through selective mRNA splicing and nuclear export.

Jekaterina Vohhodina,Angelina F Madden,Nicola Cosgrove,Kienan I Savage,Lorenzo Manti,Fabio G Liberante,Abigail L Savage,Peter Bankhead,D Paul Harkin,Eliana M Barros

doi:10.1093/nar/gkx1046

Jekaterina Vohhodina, Angelina F Madden + Show 8 more

Open Access

https://doi.org/10.1093/nar/gkx1046

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Abstract

mRNA splicing and export plays a key role in the regulation of gene expression, with recent evidence suggesting an additional layer of regulation of gene expression and cellular function through the selective splicing and export of genes within specific pathways. Here we describe a role for the RNA processing factors THRAP3 and BCLAF1 in the regulation of the cellular DNA damage response (DDR) pathway, a key pathway involved in the maintenance of genomic stability and the prevention of oncogenic transformation. We show that loss of THRAP3 and/or BCLAF1 leads to sensitivity to DNA damaging agents, defective DNA repair and genomic instability. Additionally, we demonstrate that this phenotype can be at least partially explained by the role of THRAP3 and BCLAF1 in the selective mRNA splicing and export of transcripts encoding key DDR proteins, including the ATM kinase. Moreover, we show that cancer associated mutations within THRAP3 result in deregulated processing of THRAP3/BCLAF1-regulated transcripts and consequently defective DNA repair. Taken together, these results suggest that THRAP3 and BCLAF1 mutant tumors may be promising targets for DNA damaging chemotherapy.

Highlights

RNA processing and its further translation are compartmentalized processes occurring in the nucleus and cytoplasm respectively
Recent findings from our group, as well as others, have implicated the RNA processing machinery in the regulation of the cellular DNA damage response (DDR). Consistent with this and in addition to their role in the BRCA1/BCLAF1 mRNA splicing complex previously described by our group, here we demonstrate that BCLAF1 and THRAP3 contribute to the DDR through novel RNA processing functions, which are independent of both DNA damage and BRCA1 (Figure 7)
Despite the fact that we did not observe any differential regulation of HR/Fanconi Anaemia (FA) genes regulated by THRAP3/BCLAF1 in response to DNA damage, it is possible that regulation of THRAP3/BCLAF1 following DNA damage e.g. the phosphorylation and/or PARylation events previously reported for these proteins [15,16,31], may fine tune their mRNA splicing/export functions in response to different types and/or levels of genotoxic stimuli

Summary

Introduction

RNA processing and its further translation are compartmentalized processes occurring in the nucleus and cytoplasm respectively. Pre-mRNA synthesis and maturation occurs through a multi-step process involving transcription, addition of a 5 methyl-guanine (m7G) cap, removal of intronic sequences by splicing and cleavage of the 3 end followed by polyadenylation [1], leading to the production of a stable mature RNA and facilitating its export from the nucleus for further translation [2,3]. The coupling of each successive step within the RNA synthesis/maturation pathway may serve as an additional level of control of gene expression. Recent evidence suggests multiple levels of selectivity in both mRNA splicing and export with multiple cellular processes controlled by selective splicing and export, including maintenance of pluripotency, stress responses, proliferation, survival/apoptosis, haematopoiesis and DNA repair [9,10,11]. A recent study investigating the impact of SR proteins on mRNA splicing found that the serine arginine rich (SR) mRNA-splicing proteins SRSF1–SRSF7, both contribute to the mRNA splicing of distinct groups of genes (with each SRSF protein regulating different pools of genes) and couple this selective splicing to selective mRNA export, by acting as adaptor proteins allowing the bind-

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