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Proc Natl Acad Sci U S A ; 117(6): 2894-2905, 2020 02 11.
Artigo em Inglês | MEDLINE | ID: mdl-31988137


The Mediator kinase module regulates eukaryotic transcription by phosphorylating transcription-related targets and by modulating the association of Mediator and RNA polymerase II. The activity of its catalytic core, cyclin-dependent kinase 8 (CDK8), is controlled by Cyclin C and regulatory subunit MED12, with its deregulation contributing to numerous malignancies. Here, we combine in vitro biochemistry, cross-linking coupled to mass spectrometry, and in vivo studies to describe the binding location of the N-terminal segment of MED12 on the CDK8/Cyclin C complex and to gain mechanistic insights into the activation of CDK8 by MED12. Our data demonstrate that the N-terminal portion of MED12 wraps around CDK8, whereby it positions an "activation helix" close to the T-loop of CDK8 for its activation. Intriguingly, mutations in the activation helix that are frequently found in cancers do not diminish the affinity of MED12 for CDK8, yet likely alter the exact positioning of the activation helix. Furthermore, we find the transcriptome-wide gene-expression changes in human cells that result from a mutation in the MED12 activation helix to correlate with deregulated genes in breast and colon cancer. Finally, functional assays in the presence of kinase inhibitors reveal that binding of MED12 remodels the active site of CDK8 and thereby precludes the inhibition of ternary CDK8 complexes by type II kinase inhibitors. Taken together, our results not only allow us to propose a revised model of how CDK8 activity is regulated by MED12, but also offer a path forward in developing small molecules that target CDK8 in its MED12-bound form.

Quinase 8 Dependente de Ciclina/metabolismo , Complexo Mediador/metabolismo , Domínio Catalítico , Ciclina C/genética , Ciclina C/metabolismo , Quinase 8 Dependente de Ciclina/química , Quinase 8 Dependente de Ciclina/genética , Ativação Enzimática , Humanos , Complexo Mediador/genética , Ligação Proteica , Conformação Proteica em alfa-Hélice , Domínios Proteicos
ACS Med Chem Lett ; 7(6): 595-600, 2016 Jun 09.
Artigo em Inglês | MEDLINE | ID: mdl-27326333


Using Sorafenib as a starting point, a series of potent and selective inhibitors of CDK8 was developed. When cocrystallized with CDK8 and cyclin C, these compounds exhibit a Type-II (DMG-out) binding mode.

ACS Med Chem Lett ; 7(3): 223-8, 2016 Mar 10.
Artigo em Inglês | MEDLINE | ID: mdl-26985305


Beginning with promiscuous COT inhibitors, which were found to inhibit CDK8, a series of 6-aza-benzothiophene containing compounds were developed into potent, selective CDK8 inhibitors. When cocrystallized with CDK8 and cyclin C, these compounds exhibit an unusual binding mode, making a single hydrogen bond to the hinge residue A100, a second to K252, and a key cation-π interaction with R356. Structure-based drug design resulted in tool compounds 13 and 32, which are highly potent, kinase selective, permeable compounds with a free fraction >2% and no measurable efflux. Despite these attractive properties, these compounds exhibit weak antiproliferative activity in the HCT-116 colon cancer cell line. Further examination of the activity of 32 in this cell line revealed that the compound reduced phosphorylation of the known CDK8 substrate STAT1 in a manner identical to a CDK8 knockout clone, illustrating the complex effects of inhibition of CDK8 kinase activity in proliferation in these cells.

Nature ; 526(7572): 273-276, 2015 Oct 08.
Artigo em Inglês | MEDLINE | ID: mdl-26416749


Super-enhancers (SEs), which are composed of large clusters of enhancers densely loaded with the Mediator complex, transcription factors and chromatin regulators, drive high expression of genes implicated in cell identity and disease, such as lineage-controlling transcription factors and oncogenes. BRD4 and CDK7 are positive regulators of SE-mediated transcription. By contrast, negative regulators of SE-associated genes have not been well described. Here we show that the Mediator-associated kinases cyclin-dependent kinase 8 (CDK8) and CDK19 restrain increased activation of key SE-associated genes in acute myeloid leukaemia (AML) cells. We report that the natural product cortistatin A (CA) selectively inhibits Mediator kinases, has anti-leukaemic activity in vitro and in vivo, and disproportionately induces upregulation of SE-associated genes in CA-sensitive AML cell lines but not in CA-insensitive cell lines. In AML cells, CA upregulated SE-associated genes with tumour suppressor and lineage-controlling functions, including the transcription factors CEBPA, IRF8, IRF1 and ETV6 (refs 6-8). The BRD4 inhibitor I-BET151 downregulated these SE-associated genes, yet also has anti-leukaemic activity. Individually increasing or decreasing the expression of these transcription factors suppressed AML cell growth, providing evidence that leukaemia cells are sensitive to the dosage of SE-associated genes. Our results demonstrate that Mediator kinases can negatively regulate SE-associated gene expression in specific cell types, and can be pharmacologically targeted as a therapeutic approach to AML.

Quinase 8 Dependente de Ciclina/antagonistas & inibidores , Quinases Ciclina-Dependentes/antagonistas & inibidores , Elementos Facilitadores Genéticos/genética , Regulação Neoplásica da Expressão Gênica/genética , Genes Neoplásicos/genética , Leucemia Mieloide Aguda/enzimologia , Leucemia Mieloide Aguda/genética , Animais , Proteínas de Ciclo Celular , Divisão Celular/efeitos dos fármacos , Linhagem Celular Tumoral , Linhagem da Célula/efeitos dos fármacos , Linhagem da Célula/genética , Quinase 8 Dependente de Ciclina/metabolismo , Quinases Ciclina-Dependentes/metabolismo , Progressão da Doença , Regulação para Baixo/efeitos dos fármacos , Regulação para Baixo/genética , Feminino , Regulação Neoplásica da Expressão Gênica/efeitos dos fármacos , Genes Supressores de Tumor/efeitos dos fármacos , Compostos Heterocíclicos de 4 ou mais Anéis/farmacologia , Humanos , Leucemia Mieloide Aguda/tratamento farmacológico , Leucemia Mieloide Aguda/patologia , Masculino , Camundongos , Camundongos Endogâmicos , Camundongos SCID , Proteínas Nucleares/antagonistas & inibidores , Compostos Policíclicos/farmacologia , Fatores de Transcrição/antagonistas & inibidores , Fatores de Transcrição/biossíntese , Fatores de Transcrição/genética , Regulação para Cima/efeitos dos fármacos , Regulação para Cima/genética
Proc Natl Acad Sci U S A ; 110(20): 8081-6, 2013 May 14.
Artigo em Inglês | MEDLINE | ID: mdl-23630251


In contrast with the very well explored concept of structure-activity relationship, similar studies are missing for the dependency between binding kinetics and compound structure of a protein ligand complex, the structure-kinetic relationship. Here, we present a structure-kinetic relationship study of the cyclin-dependent kinase 8 (CDK8)/cyclin C (CycC) complex. The scaffold moiety of the compounds is anchored in the kinase deep pocket and extended with diverse functional groups toward the hinge region and the front pocket. These variations can cause the compounds to change from fast to slow binding kinetics, resulting in an improved residence time. The flip of the DFG motif ("DMG" in CDK8) to the inactive DFG-out conformation appears to have relatively little influence on the velocity of binding. Hydrogen bonding with the kinase hinge region contributes to the residence time but has less impact than hydrophobic complementarities within the kinase front pocket.

Ciclina C/química , Quinase 8 Dependente de Ciclina/química , Motivos de Aminoácidos , Domínio Catalítico , Cristalografia por Raios X , Desenho de Fármacos , Humanos , Ligação de Hidrogênio , Cinética , Ligantes , Modelos Moleculares , Ligação Proteica , Conformação Proteica , Sais/química , Temperatura , Fatores de Tempo