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RAD51D splice variants and cancer-associated mutations reveal XRCC2 interaction to be critical for homologous recombination.

ABSTRACT: The proficiency of cancer cells to repair DNA double-strand breaks (DSBs) by homologous recombination (HR) is a key determinant in predicting response to targeted therapies such as PARP inhibitors. The RAD51 paralogs work as multimeric complexes and act downstream of BRCA1 to facilitate HR. Numerous epidemiological studies have linked RAD51 paralog mutations with hereditary cancer predisposition. Despite their substantial links to cancer, RAD51 paralog HR function has remained elusive. Here we identify isoform 1 as the functional isoform of RAD51D, whereas isoform 4 which has a large N-terminal deletion (including the Walker A motif), and isoform 6 which includes an alternate exon in the N-terminus, are non-functional. To determine the importance of this N-terminal region, we investigated the impact of cancer-associated mutations and SNPs in this variable RAD51D N-terminal region using yeast-2-hybrid and yeast-3-hybrid assays to screen for altered protein-protein interactions. We identified two cancer-associated mutations close to or within the Walker A motif (G96C and G107?V, respectively) that independently disrupt RAD51D interaction with XRCC2. We validated our yeast interaction data in human U2OS cells by co-immunoprecipitation and determined the impact of these mutations on HR-proficiency using a sister chromatid recombination reporter assay in a RAD51D knock-out cell line. Our investigation reveals that the interaction of RAD51D with XRCC2 is required for DSB repair. By characterizing the impact of cancer-associated mutations on RAD51D interactions, we aim to develop predictive models for therapeutic sensitivity and resistance in patients who harbor similar mutations in RAD51D.

SUBMITTER: Baldock RA

PROVIDER: S-EPMC6508892 | biostudies-literature | 2019 Apr

REPOSITORIES: biostudies-literature

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RAD51D splice variants and cancer-associated mutations reveal XRCC2 interaction to be critical for homologous recombination.

Baldock Robert A RA Pressimone Catherine A CA Baird Jared M JM Khodakov Anton A Luong Thong T TT Grundy McKenzie K MK Smith Chelsea M CM Karpenshif Yoav Y Bratton-Palmer Dominique S DS Prakash Rohit R Jasin Maria M Garcin Edwige B EB Gon Stéphanie S Modesti Mauro M Bernstein Kara A KA

DNA repair 20190223

The proficiency of cancer cells to repair DNA double-strand breaks (DSBs) by homologous recombination (HR) is a key determinant in predicting response to targeted therapies such as PARP inhibitors. The RAD51 paralogs work as multimeric complexes and act downstream of BRCA1 to facilitate HR. Numerous epidemiological studies have linked RAD51 paralog mutations with hereditary cancer predisposition. Despite their substantial links to cancer, RAD51 paralog HR function has remained elusive. Here we i ...[more]

PMID: 30836272

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Project description:BACKGROUND: The homologous recombination (HR) pathway is vital for maintaining genomic integrity through the restoration of double-stranded breaks and interstrand crosslinks. The RAD51 paralogs (RAD51B, RAD51C, RAD51D, XRCC2, XRCC3) are essential for this process in vertebrates, and the RAD51D paralog is unique in that it participates in both HR repair and telomere maintenance. RAD51D is also known to directly interact with the RAD51C and XRCC2 proteins. Rad51d splice variants have been reported in mouse and human tissues, supportive of a role for alternative splicing in HR regulation. The present study evaluated the interaction of the Rad51d splice isoform products with RAD51C and XRCC2 and their expression patterns. RESULTS: Yeast-2-hybrid analysis was used to determine that the Mus musculus Rad51d splice variant product RAD51DDelta7b (deleted for residues 219 through 223) was capable of interacting with both RAD51C and XRCC2 and that RAD51D+int3 interacted with XRCC2. In addition, the linker region (residues 54 through 77) of RAD51D was identified as a region that potentially mediates binding with XRCC2. Cellular localization, detected by EGFP fusion proteins, demonstrated that each of the splice variant products tested was distributed throughout the cell similar to the full-length protein. However, none of the splice variants were capable of restoring resistance of Rad51d-deficient cell lines to mitomycin C. RT-PCR expression analysis revealed that Rad51dDelta3 (deleted for exon 3) and Rad51dDelta5 (deleted for exon 5)transcripts display tissue specific expression patterns with Rad51dDelta3 being detected in each tissue except ovary and Rad51dDelta5 not detected in mammary gland and testis. These expression studies also led to the identification of two additional Rad51d ubiquitously expressed transcripts, one deleted for both exon 9 and 10 and one deleted for only exon 10. CONCLUSION: These results suggest Rad51d alternative splice variants potentially modulate mechanisms of HR by sequestering either RAD51C or XRCC2.

Dataset Information

RAD51D splice variants and cancer-associated mutations reveal XRCC2 interaction to be critical for homologous recombination.

Publications

RAD51D splice variants and cancer-associated mutations reveal XRCC2 interaction to be critical for homologous recombination.

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