NFBD1/KIAA0170 is a chromatin-associated protein involved in DNA damage signaling pathways

NFBD1/KIAA0170 is a (n) under bar uclear (f) under bar actor with an N-terminal FHA ((f) under bar ork (h) under bar ead-(a) under bar ssociated) domain and a tandem repeat of (B) under bar RCT ((b) under bar reast (c) under bar ancer susceptibility gene-1 C (t) under bar erminus) (d) under bar omains, both of which are present in a number of proteins involved in DNA repair and/or DNA damage signaling pathways. We have investigated the association of NFBD1 with DNA damage responses. We found that the NFBD1 transcript is abundant in the testis relative to other tissues. NFBD1 is a chromatin-associated protein and is modified in G(2)/M phase or after DNA damage. NFBD1 phosphorylation in response to ionizing radiation (IR) was ATM-dependent. NFBD1 exhibited diffuse nuclear staining in the majority of untreated cells analyzed by indirect immunofluorescence and formed discrete nuclear foci after exposure to IR, UV radiation, and hydroxyurea treatment. IR induced NFBD1 foci within 1 min. The foci colocalized with gamma-H2AX foci, which have been previously shown to localize at sites of DNA double-strand breaks. IR-induced NFBD1 foci also colocalized with 53BP1 and MRE11/RADD50 foci. Taken together, these results suggest that NFBD1 is a mediator of DNA damage-dependent signaling.