RESUMO
Mediator kinases (CDK8/19) are transcriptional regulators broadly implicated in cancer. Despite their central role in fine-tuning gene-expression programs, we find complete loss of CDK8/19 is tolerated in colorectal cancer (CRC) cells. Using orthogonal functional genomic and pharmacological screens, we identify BET protein inhibition as a distinct vulnerability in CDK8/19-depleted cells. Combined CDK8/19 and BET inhibition led to synergistic growth retardation in human and mouse models of CRC. Strikingly, depletion of CDK8/19 in these cells led to global repression of RNA polymerase II (Pol II) promoter occupancy and transcription. Concurrently, loss of Mediator kinase led to a profound increase in MED12 and BRD4 co-occupancy at enhancer elements and increased dependence on BET proteins for the transcriptional output of cell-essential genes. In total, this work demonstrates a synthetic lethal interaction between Mediator kinase and BET proteins and exposes a therapeutic vulnerability that can be targeted using combination therapies.
Assuntos
Proteínas de Ciclo Celular/metabolismo , Proliferação de Células , Neoplasias Colorretais/enzimologia , Quinase 8 Dependente de Ciclina/metabolismo , Quinases Ciclina-Dependentes/metabolismo , Complexo Mediador/metabolismo , Proteínas Nucleares/metabolismo , Fatores de Transcrição/metabolismo , Adulto , Idoso , Idoso de 80 Anos ou mais , Animais , Protocolos de Quimioterapia Combinada Antineoplásica/uso terapêutico , Sítios de Ligação , Proteínas de Ciclo Celular/antagonistas & inibidores , Proteínas de Ciclo Celular/genética , Proliferação de Células/efeitos dos fármacos , Neoplasias Colorretais/tratamento farmacológico , Neoplasias Colorretais/genética , Quinase 8 Dependente de Ciclina/genética , Quinases Ciclina-Dependentes/genética , Elementos Facilitadores Genéticos , Feminino , Regulação Neoplásica da Expressão Gênica , Células HCT116 , Humanos , Masculino , Complexo Mediador/antagonistas & inibidores , Complexo Mediador/genética , Camundongos Endogâmicos BALB C , Camundongos Knockout , Camundongos Nus , Proteínas do Tecido Nervoso/antagonistas & inibidores , Proteínas do Tecido Nervoso/genética , Proteínas do Tecido Nervoso/metabolismo , Proteínas Nucleares/antagonistas & inibidores , Proteínas Nucleares/genética , Inibidores de Proteínas Quinases/farmacologia , Receptores de Superfície Celular/antagonistas & inibidores , Receptores de Superfície Celular/genética , Receptores de Superfície Celular/metabolismo , Transdução de Sinais , Fatores de Transcrição/antagonistas & inibidores , Fatores de Transcrição/genética , Transcrição Gênica , Carga Tumoral , Ensaios Antitumorais Modelo de XenoenxertoRESUMO
Initiation and maintenance of transcriptional states are critical for controlling normal tissue homeostasis and differentiation. The cyclin dependent kinases CDK8 and CDK19 (Mediator kinases) are regulatory components of Mediator, a highly conserved complex that orchestrates enhancer-mediated transcriptional output. While Mediator kinases have been implicated in the transcription of genes necessary for development and growth, its function in mammals has not been well defined. Using genetically defined models and pharmacological inhibitors, we showed that CDK8 and CDK19 function in a redundant manner to regulate intestinal lineage specification in humans and mice. The Mediator kinase module bound and phosphorylated key components of the chromatin remodeling complex switch/sucrose non-fermentable (SWI/SNF) in intestinal epithelial cells. Concomitantly, SWI/SNF and MED12-Mediator colocalized at distinct lineage-specifying enhancers in a CDK8/19-dependent manner. Thus, these studies reveal a transcriptional mechanism of intestinal cell specification, coordinated by the interaction between the chromatin remodeling complex SWI/SNF and Mediator kinase.