RESUMO
Cancer progression is associated with epigenetic alterations, such as changes in DNA methylation, histone modifications or variants incorporation. The p400 ATPase, which can incorporate the H2A.Z variant, and the Tip60 histone acetyltransferase are interacting chromatin-modifying proteins crucial for the control of cell proliferation. We demonstrate here that Tip60 acts as a tumor suppressor in colon, since mice heterozygous for Tip60 are more susceptible to chemically induced preneoplastic lesions and adenomas. Strikingly, heterozygosity for p400 reverses the Tip60-dependent formation of preneoplastic lesions, uncovering for the first time pro-oncogenic functions for p400. By genome-wide analysis and using a specific inhibitor in vivo, we demonstrated that these effects are dependent on Wnt signaling which is antagonistically impacted by p400 and Tip60: p400 directly favors the expression of a subset of Wnt-target genes and regulators, whereas Tip60 prevents ß-catenin acetylation and activation. Taken together, our data underline the physiopathological importance of interplays between chromatin-modifying enzymes in the control of cancer-related signaling pathways.
Assuntos
Neoplasias do Colo/metabolismo , Neoplasias do Colo/patologia , Histona Acetiltransferases/fisiologia , Histonas/metabolismo , Receptores de Inositol 1,4,5-Trifosfato/fisiologia , Transativadores/fisiologia , Proteínas Wnt/metabolismo , Acetilação , Animais , Western Blotting , Células Cultivadas , Cromatina/metabolismo , Imunoprecipitação da Cromatina , Neoplasias do Colo/genética , Progressão da Doença , Feminino , Perfilação da Expressão Gênica , Histona Acetiltransferases/metabolismo , Lisina Acetiltransferase 5 , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Lesões Pré-Cancerosas/genética , Lesões Pré-Cancerosas/metabolismo , Lesões Pré-Cancerosas/patologia , Processamento de Proteína Pós-Traducional , RNA Mensageiro/genética , Reação em Cadeia da Polimerase em Tempo Real , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Proteínas Wnt/genética , beta Catenina/metabolismoRESUMO
The p400 E1A-associated protein, which mediates H2A.Z incorporation at specific promoters, plays a major role in cell fate decisions: it promotes cell cycle progression and inhibits induction of apoptosis or senescence. Here, we show that p400 expression is required for the correct control of ROS metabolism. Depletion of p400 indeed increases intracellular ROS levels and causes the appearance of DNA damage, indicating that p400 maintains oxidative stress below a threshold at which DNA damages occur. Suppression of the DNA damage response using a siRNA against ATM inhibits the effects of p400 on cell cycle progression, apoptosis, or senescence, demonstrating the importance of ATM-dependent DDR pathways in cell fates control by p400. Finally, we show that these effects of p400 are dependent on direct transcriptional regulation of specific promoters and may also involve a positive feedback loop between oxidative stress and DNA breaks since we found that persistent DNA breaks are sufficient to increase ROS levels. Altogether, our results uncover an unexpected link between p400 and ROS metabolism and allow deciphering the molecular mechanisms largely responsible for cell proliferation control by p400.
