RESUMEN
Although the roles of DNA-dependent protein kinase catalytic subunits (DNA-PKcs) in the non-homologous end joining (NHEJ) of DNA repair are well-recognized, the biological mechanisms and regulators by DNA-PKcs besides DNA repair, have not been clearly described. Here, we show that active DNA-PKcs caused by ionizing radiation, phosphorylated Snail1 at serine (Ser) 100, led to increased Snail1 stability. Furthermore, phosphorylated Snail1 at Ser100 reciprocally inhibited the kinase activity of DNA-PKcs, resulting in an inhibition of DNA repair activity. Moreover, Snail1 phosphorylation by DNA-PKcs was involved in genomic instability and aggressive tumor characteristics. Our results describe novel cellular mechanisms that affect genomic instability, sensitivity to DNA-damaging agents, and the migration of tumor cells by reciprocal regulation between DNA-PKcs and Snail1.
Asunto(s)
Proteína Quinasa Activada por ADN/metabolismo , Inestabilidad Genómica , Factores de Transcripción/metabolismo , Línea Celular Tumoral , Aberraciones Cromosómicas/efectos de la radiación , Reparación del ADN por Unión de Extremidades/efectos de la radiación , Proteína Quinasa Activada por ADN/antagonistas & inhibidores , Proteína Quinasa Activada por ADN/genética , Inestabilidad Genómica/efectos de la radiación , Humanos , Células MCF-7 , Masculino , Fosforilación , Unión Proteica , Estabilidad Proteica , Subunidades de Proteína/antagonistas & inhibidores , Subunidades de Proteína/genética , Subunidades de Proteína/metabolismo , Interferencia de ARN , ARN Interferente Pequeño/metabolismo , Radiación Ionizante , Factores de Transcripción de la Familia Snail , Factores de Transcripción/antagonistas & inhibidores , Factores de Transcripción/genéticaRESUMEN
Although cyclin G1 has been implicated in certain p53-related biological phenomena, other aspects of its function remain unclear. Here we report hitherto unknown mechanism by which cyclin G1 increases radiation sensitivity by regulating the level of cyclin B1. Overexpression of cyclin G1 was observable in lung carcinoma tissues. Irradiation of human lung cells with cyclin G1 overexpression resulted in increased cell death and gamma-H2AX foci suggesting that cyclin G1 rendered the cells more susceptible to DNA damage. Enhanced radiosensitivity by cyclin G1 was correlated with increased cyclin B1, CDC2/cyclin B1 complex, and MPM2. Cell cycle synchronization clearly showed coexpression of cyclin G1 and cyclin B1 in G2/M phase. Depletion of cyclin G1 by interference RNA revealed that cyclin G1 regulated transcription of cyclin B1 in a p53-independent manner, and confirmed that the increased mitotic cells and cell death by cyclin G1 were dependent upon cyclin B1. Therefore, our data suggest that cyclin G1 enhanced radiation sensitivity by overriding radiation-induced G2 arrest through transcriptional upregulation of cyclin B1.