TRIM29 is required for efficient recruitment of 53BP1 in response to DNA double-strand breaks in vertebrate cells.

Tripartite motif-containing protein 29 (TRIM29) is involved in DNA double-strand break (DSB) repair. However, the specific roles of TRIM29 in DNA repair are not clearly understood. To investigate the involvement of TRIM29 in DNA DSB repair, we disrupted TRIM29 in DT40 cells by gene targeting with homologous recombination (HR). The roles of TRIM29 were investigated by clonogenic survival assays and immunofluorescence analyses. TRIM29 triallelic knockout (TRIM29) cells were sensitive to etoposide, but resistant to camptothecin. Foci formation assays to assess DNA repair activities showed that the dissociation of etoposide-induced phosphorylated H2A histone family member X (ɣ-H2AX) foci was retained in TRIM29 cells, and the formation of etoposide-induced tumor suppressor p53-binding protein 1 (53BP1) foci in TRIM29 cells was slower compared with wild-type (WT) cells. Interestingly, the kinetics of camptothecin-induced RAD51 foci formation of TRIM29 cells was higher than that of WT cells. These results indicate that TRIM29 is required for efficient recruitment of 53BP1 to facilitate the nonhomologous end-joining (NHEJ) pathway and thereby suppress the HR pathway in response to DNA DSBs. TRIM29 regulates the choice of DNA DSB repair pathway by facilitating 53BP1 accumulation to promote NHEJ and may have potential for development into a therapeutic target to sensitize refractory cancers or as biomarker of personalized therapies.