RESUMEN
Genomic instability, a hallmark of cancer, is commonly caused by failures in the DNA damage response. Here we conducted a bioinformatical screen to reveal DNA damage response genes that are upregulated by estrogen and highly mutated in breast and ovarian cancers. This screen identified 53 estrogen-dependent cancer genes, some of which are novel. Notably, the screen retrieved 9 DNA helicases as well as 5 nucleases. DNA2, which functions as both a helicase and a nuclease and plays a role in DNA repair and replication, was retrieved in the screen. Mutations in DNA2, found in estrogen-dependent cancers, are clustered in the helicase and nuclease domains, suggesting activity impairment. Indeed, we show that mutations found in ovarian cancers impair DNA2 activity. Depletion of DNA2 in cells reduces their tumorogenicity in mice. In human, high expression of DNA2 correlates with poor survival of estrogen receptor-positive patients but not of estrogen receptor-negative patients. We also demonstrate that depletion of DNA2 in cells reduces proliferation, while addition of estrogen restores proliferation. These findings suggest that cells responding to estrogen will proliferate despite impaired in DNA2 activity, potentially promoting genomic instability and triggering cancer development.
Asunto(s)
Neoplasias de la Mama/genética , ADN Helicasas/genética , Reparación del ADN/genética , Estrógenos/farmacología , Neoplasias Ováricas/genética , Animales , Neoplasias de la Mama/mortalidad , Línea Celular Tumoral , Proliferación Celular/efectos de los fármacos , Proliferación Celular/genética , Transformación Celular Neoplásica/genética , Daño del ADN/genética , ADN Helicasas/biosíntesis , Femenino , Inestabilidad Genómica/genética , Humanos , Células MCF-7 , Ratones , Ratones Endogámicos NOD , Ratones SCID , Mutación , Trasplante de Neoplasias , Neoplasias Ováricas/mortalidad , Interferencia de ARN , ARN Interferente Pequeño , Receptores de Estrógenos/metabolismo , Trasplante HeterólogoRESUMEN
To avoid genomic instability, cells have developed surveillance mechanisms such as the spindle assembly checkpoint (SAC) and the DNA damage response. ATM and MDC1 are central players of the cellular response to DNA double-strand breaks. Here, we identify a new role for these proteins in the regulation of mitotic progression and in SAC activation. MDC1 localizes at mitotic kinetochores following SAC activation in an ATM-dependent manner. ATM phosphorylates histone H2AX at mitotic kinetochores, and this phosphorylation is required for MDC1 localization at kinetochores. ATM and MDC1 are needed for kinetochore localization of the inhibitory mitotic checkpoint complex components, Mad2 and Cdc20, and for the maintenance of the mitotic checkpoint complex integrity. This probably relies on the interaction of MDC1 with the MCC. In this work, we have established that ATM and MDC1 maintain genomic stability not only by controlling the DNA damage response, but also by regulating SAC activation, providing an important link between these two essential biological processes.
