Chromosomal translocations typically impair cell differentiation and often require secondary mutations for malignant transformation. However, the role of a primary translocation in the development of collaborating mutations is debatable. To delineate the role of leukemic translocation NUP98-HOXD13 (NHD13) in secondary mutagenesis, DNA break and repair mechanisms in stimulated mouse B lymphocytes expressing NHD13 were analyzed. Our results showed significantly reduced expression of non-homologous end joining (NHEJ)-mediated DNA repair genes, DNA Pkcs, DNA ligase4, and Xrcc4 leading to cell cycle arrest at G2/M phase. Our results showed that expression of NHD13 fusion gene resulted in impaired NHEJ-mediated DNA break repair.