RESUMO
In response to DNA damage, several signaling pathways that arrest the cell cycle in G(1) and G(2) are activated. The down-regulation of mitotic genes contributes to the stable maintenance of the G(2) arrest. The human LINC or DREAM complex, together with the B-MYB transcription factor, plays an essential role in the expression of G(2)-M genes. Here, we show that DNA damage results in the p53-dependent binding of p130 and E2F4 to LINC and the dissociation of B-MYB from LINC. We find that B-MYB fails to dissociate from LINC in p53 mutant cells, that this contributes to increased G(2)-M gene expression in response to DNA damage in these cells, and, importantly, that B-MYB is required for recovery from the G(2) DNA damage checkpoint in p53-negative cells. Reanalysis of microarray expression data sets revealed that high levels of B-MYB correlate with a p53 mutant status and an advanced tumor stage in primary human breast cancer. Taken together, these data suggest that B-MYB/LINC plays an important role in the DNA damage response downstream of p53.
Assuntos
Proteínas de Ciclo Celular/metabolismo , Dano ao DNA , Mutação , Transativadores/metabolismo , Proteína Supressora de Tumor p53/metabolismo , Neoplasias da Mama/genética , Neoplasias da Mama/metabolismo , Neoplasias da Mama/patologia , Proteínas de Ciclo Celular/genética , Linhagem Celular Tumoral , Proteína Substrato Associada a Crk/metabolismo , Doxorrubicina/farmacologia , Fase G2/genética , Células HCT116 , Humanos , Proteínas Interatuantes com Canais de Kv/metabolismo , Proteínas Nucleares/metabolismo , Ligação Proteica , Proteínas Repressoras/metabolismo , Transativadores/genética , Proteína Supressora de Tumor p53/genética , Proteínas Supressoras de Tumor/metabolismoRESUMO
Here we report the identification of the LIN complex (LINC), a human multiprotein complex that is required for transcriptional activation of G2/M genes. LINC is related to the recently identified dREAM and DRM complexes of Drosophila and C. elegans that contain homologs of the mammalian retinoblastoma tumor suppressor protein. The LINC core complex consists of at least five subunits including the chromatin-associated LIN-9 and RbAp48 proteins. LINC dynamically associates with pocket proteins, E2F and B-MYB during the cell cycle. In quiescent cells, LINC binds to p130 and E2F4. During cell cycle entry, E2F4 and p130 dissociate and LINC switches to B-MYB and p107. Chromatin Immunoprecipitation experiments demonstrate that LINC associates with a large number of E2F-regulated promoters in quiescent cells. However, RNAi experiments reveal that LINC is not required for repression. In S-phase, LINC selectively binds to the promoters of G2/M genes whose products are required for mitosis and plays an important role in their cell cycle dependent activation.
