NBN and neoplasm: Since the disruption of the Mre11 binding domain of Nbs1 may lead to loss of Mre11 nuclear localization and increased staining for Mre11 in the cytoplasm [21], we were able to analyze the functional consequences of the three NBS1 mutations located in the Mre11-binding domain by the analysis of nuclear localization of Mre11 in tumor cells.