Haploinsufficiency of RAD51B Causes Centrosome Fragmentation and Aneuploidy in Human Cells

Abstract

The Rad51-like proteins, Rad51B, Rad51C, Rad51D, XRCC2, and XRCC3, have been shown to form two distinct complexes and seem to assist Rad51 in the early stages of homologous recombination. Although these proteins share sequence similarity with Rad51, they do not show functional redundancy. Among them, Rad51B is unique in that the gene maps to the human chromosome 14q23-24, the region frequently involved in balanced chromosome translocations in benign tumors particularly in uterine leiomyomas. Despite accumulating descriptive evidence of altered Rad51B function in these tumors, the biological significance of this aberration is still unknown. To assess the significance of reduced Rad51B function, we deleted the gene in the human colon cancer cell line HCT116 by gene targeting. Here, we show that haploinsufficiency of RAD51B causes mild hypersensitivity to DNAdamaging agents, a mild reduction in sister chromatid exchange, impaired Rad51 focus formation, and an increase in chromosome aberrations. Remarkably, haploinsufficiency of RAD51B leads to centrosome fragmentation and aneuploidy. In addition, an f50% reduction in RAD51B mRNA levels by RNA interference also leads to centrosome fragmentation in the human fibrosarcoma cell line HT1080. These findings suggest that the proper biallelic expression of RAD51B is required for the maintenance of chromosome integrity in human cells. (Cancer Res 2006; 66(12): 6018-24)

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

“…1). Consistent with previous studies (39,44), the RAD51B knockdown MCF7 cells exhibited a comparable reduction in RAD51 foci formation on the DSB sites after ionizing radiation (Fig. 1, B and C).…”

“…RAD51B-deficient cells are hypersensitive to DSB-inducing agents, such as cisplatin, mitomycin C (MMC), and ␥-rays, indicating that the RAD51B protein is involved in the HRR pathway (39 -44). Genetic experiments revealed that RAD51B-deficient cells exhibited impaired RAD51 assembly onto DSB sites (39,44), suggesting that the RAD51B protein functions in the early stage of the HRR pathway. Biochemical experiments also suggested that the RAD51B protein participates in the early to late stages of the HRR pathway (45)(46)(47).…”

Radiation-induced mitotic catastrophe in PARG-deficient cells

“…However, 48 hours after irradiation, the proportion of cells with fragmented centrosomes was similar to the level observed for both unirradiated cell lines. Taken together, these results indicate that depletion of PARG exacerbates the centrosome amplification and fragmentation that has been already described in irradiated cells, in cells deficient in proteins involved in DSB repair or in cells overexpressing PARP3 and treated with an alkylating agent (Augustin et al, 2003;Date et al, 2006;Griffin et al, 2000).…”

Inactivation of the Nijmegen Breakage Syndrome Gene Leads to Excess Centrosome Duplication via the ATR/BRCA1 Pathway

“…A growing body of evidence suggests that aneuploidy is often caused by chromosomal instability during mitosis (3,4), which may result from an improper duplication of centrosomes. The centrosome organizes the spindles for the separation of chromosomes during mitosis, and the presence of more than two centrosomes in a cell can result in lost chromosomes or in an excess number of chromosomes (2,5).…”