The role of NBS1 for cellular response after UV irradiation

Abstract

Nijmegen breakage syndrome (NBS), characterized by high sensitivity to ionizing radiation and predisposition to lymphoid cancer, is phenotypically similar to Ataxia telangiectasia. It is well known that NBS1, the protein responsible for NBS, is cooperative with ATM for IR-induced DNA damage response such as double-strand break repair and cell cycle checkpoints. Recently, it was also reported that NBS shares common clinical signs with ATR-defective Seckel syndrome, such as microcephaly and NBS1 activates ATR. Since ATR functions in stalled replication fork after HU treatment or UV exposure, NBS1 might have potential roles in a response to UV damage. However, the function of NBS1 at S phase is unknown. Our result showed that NBS cells were high sensitivity to UV and NBS1 accumulated in the stalled replication fork. Moreover UV-induced PCNA mono-ubiquitination and pol eta foci were not observed in NBS cells. These results indicated that NBS1 might promote the UV damage response.