Role of FANCD2 in the response of DNA damage after UV irradiation

MB FEDERICO, MB VALLERGA, A RADL, G SORIA, S, M DIGIORGIO, JL BOCCO, V GOTTIFREDI

Buenos aires

Conferencia; EMBO Conference: Ubiquitin & ubiquitin-like proteins: At the crossroads from chromatin to protein; 2014

EMBO Meetings

Fanconi Anemia (FA) is a rare autosomal recessive disease characterized by multiple congenital abnormalities, progressive bone marrow failure, and cancer predisposition. FA patient-derived cells are hypersensitive to agents such as mitomycin C (MMC) or diepoxybutane (DEB) which cause the accumulation of highly toxic DNA cross-links between two DNA strands (inter-strand crosslinks- ICLs). FA research has therefore focused in the understanding of FA activation after treatments such as MMC. However, the broad failure in tissue homeostasis characteristic of FA patients indicates that the FA pathway might aid DNA replication across a broader range of DNA lesions. In fact, the FA pathway is activated during unperturbed S phase, suggesting that such FA activation might happen at replication forks that encounter endogenously generated DNA lesion. FA activation was reported after many different stress signals including UV irradiation. However, a yet undiscovered role of FA in the cellular response to UV irradiation is certainly suggested by the frequent formation of café-au-lait spots in the skin of FA patient (usually used as a clinical manifestation that aids diagnosis). Given the reduced information available regarding the role of the FA pathway in the UV response we decided to explore the role of the central FA component, FANCD2 in the response to UV irradiation. As reported by others, we observed that FANCD2 ubiquitination and focal organization are upregulated after UV irradiation of U2OS osteosarcoma cells. Intriguingly, when depleting FANCD2 by transiently transfecting a specific siRNA we observed no contribution of FANCD2 to cell survival after UV irradiation but a strong contribution to genomic stability as revealed by micronuclei and radial chromosome accumulation. This demonstrates that FANCD2 participates in the cellular response to UV irradiation, specifically by protecting genomic stability. This also reveals a versatile involvement of the FA pathway in the detection and management of DNA replication barriers of different source, which might unmask important aspects of the etiology of FA cancer predisposition.