Recombination Activator Function of the Novel RAD51- and RAD51B-binding Protein, Human EVL

Abstract

The RAD51 protein is a central player in homologous recombinational repair. The RAD51B protein is one of five RAD51 paralogs that function in the homologous recombinational repair pathway in higher eukaryotes. In the present study, we found that the human EVL (Ena/Vasp-like) protein, which is suggested to be involved in actin-remodeling processes, unexpectedly binds to the RAD51 and RAD51B proteins and stimulates the RAD51-mediated homologous pairing and strand exchange. The EVL knockdown cells impaired RAD51 assembly onto damaged DNA after ionizing radiation or mitomycin C treatment. The EVL protein alone promotes single-stranded DNA annealing, and the recombination activities of the EVL protein are further enhanced by the RAD51B protein. The expression of the EVL protein is not ubiquitous, but it is significantly expressed in breast cancer-derived MCF7 cells. These results suggest that the EVL protein is a novel recombination factor that may be required for repairing specific DNA lesions, and that may cause tumor malignancy by its inappropriate expression.Chromosomal DNA double strand breaks (DSBs) 2 are potential inducers of chromosomal aberrations and tumorigenesis, and they are accurately repaired by the homologous recombinational repair (HRR) pathway, without base substitutions, deletions, and insertions (1-3). In the HRR pathway (4, 5), single-stranded DNA (ssDNA) tails are produced at the DSB sites. The RAD51 protein, a eukaryotic homologue of the bacterial RecA protein, binds to the ssDNA tail and forms a helical nucleoprotein filament. The RAD51-ssDNA filament then binds to the intact double-stranded DNA (dsDNA) to form a threecomponent complex, containing ssDNA, dsDNA, and the RAD51 protein. In this three-component complex, the RAD51 protein promotes recombination reactions, such as homologous pairing and strand exchange (6 -9).The RAD51 protein requires auxiliary proteins to promote the homologous pairing and strand exchange reactions efficiently in cells (10 -12). In humans, the RAD52, RAD54, and RAD54B proteins directly interact with the RAD51 protein (13-17) and stimulate the RAD51-mediated homologous pairing and/or strand exchange reactions in vitro (18 -21). The human RAD51AP1 protein, which directly binds to the RAD51 protein (22), was also found to stimulate RAD51-mediated homologous pairing in vitro (23, 24). The BRCA2 protein contains ssDNA-binding, dsDNA-binding, and RAD51-binding motifs (25)(26)(27)(28)(29)(30)(31)(32)(33), and the Ustilago maydis BRCA2 ortholog, Brh2, reportedly stimulated RAD51-mediated strand exchange (34,35). Most of these RAD51-interacting factors are known to be required for efficient RAD51 assembly onto DSB sites in cells treated with ionizing radiation (10 -12).The RAD51B (RAD51L1, Rec2) protein is a member of the RAD51 paralogs, which share about 20 -30% amino acid sequence similarity with the RAD51 protein (36 -38). RAD51B-deficient cells are hypersensitive to DSB-inducing agents, such as cisplatin, mitomycin C (MMC), and ␥-rays, indicating that the RAD51B protei...

Novel Genetic Markers of Breast Cancer Survival Identified by a Genome-Wide Association Study

“…Over-expression of this gene has been shown to cause cell cycle delay and apoptosis (27, 28). The RAD51L1 gene is not ubiquitously expressed, but it is significantly expressed in breast cancer-derived MCF7 cells (29). A recent GWAS identified a SNP in this gene, rs999737, to be associated with breast cancer risk (16).…”

Recognition, signaling, and repair of DNA double-strand breaks produced by ionizing radiation in mammalian cells: The molecular choreography

“…PSF is also reported to interact directly with RAD51D in vitro and to play a role in maintaining sister chromatid cohesion [1193]. Additional proteins that interact with RAD51 and its paralogs are being identified [1194].…”

Fine mapping of 14q24.1 breast cancer susceptibility locus

“…Molecular studies of the RAD51L1 protein suggest its main function is to promote homologous recombination repair; specifically, the protein contributes to genome integrity maintenance in response to UV-induced damages (Havre et al 1998; Takata et al 2000). In breast cell lines, it has been shown that both transcription and protein levels of RAD51L1 are down-regulated by over-expression of EZH2, a transcriptional repressor previously linked to aggressive and metastatic breast cancers; RAD51L1 may also partner with the protein EVL (Ena/Vasp-like) to stimulate inappropriate RAD51-mediated recombination in breast cancer cell lines (Takaku et al 2009; Zeidler et al 2005). …”