RESUMO
Aurora kinases are essential for chromosomal segregation and cell division and thereby important for maintaining the proper genomic integrity. There are three classes of aurora kinases in humans: A, B, and C. Aurora kinase A is frequently overexpressed in various cancers. The link of the overexpression and tumorigenesis is yet to be understood. By employing virtual screening, we have found that anacardic acid, a pentadecane aliphatic chain containing hydroxylcarboxylic acid, from cashew nut shell liquid could be docked in Aurora kinases A and B. Remarkably, we found that anacardic acid could potently activate the Aurora kinase A mediated phosphorylation of histone H3, but at a similar concentration the activity of aurora kinase B remained unaffected in vitro. Mechanistically, anacardic acid induces the structural changes and also the autophosphorylation of the aurora kinase A to enhance the enzyme activity. This data thus indicate anacardic acid as the first small-molecule activator of Aurora kinase, which could be highly useful for probing the function of hyperactive (overexpressed) Aurora kinase A.
Assuntos
Ácidos Anacárdicos/química , Ativadores de Enzimas/química , Proteínas Serina-Treonina Quinases/química , Ácidos Anacárdicos/isolamento & purificação , Anacardium , Aurora Quinase A , Aurora Quinase B , Aurora Quinases , Linhagem Celular , Clonagem Molecular , Cristalografia por Raios X , Ativadores de Enzimas/isolamento & purificação , Histonas/química , Humanos , Cinética , Modelos Moleculares , Estrutura Molecular , Fosforilação , Proteínas Serina-Treonina Quinases/genética , Espectrometria de FluorescênciaRESUMO
Reversible acetylation of histone and nonhistone proteins plays pivotal role in cellular homeostasis. Dysfunction of histone acetyltransferases (HATs) leads to several diseases including cancer, neurodegenaration, asthma, diabetes, AIDS, and cardiac hypertrophy. We describe the synthesis and characterization of a set of p300-HAT-specific small-molecule inhibitors from a natural nonspecific HAT inhibitor, garcinol, which is highly toxic to cells. We show that the specific inhibitor selectively represses the p300-mediated acetylation of p53 in vivo. Furthermore, inhibition of p300-HAT down regulates several genes but significantly a few important genes are also upregulated. Remarkably, these inhibitors were found to be nontoxic to T cells, inhibit histone acetylation of HIV infected cells, and consequently inhibit the multiplication of HIV.
Assuntos
Fármacos Anti-HIV , Proteínas de Ciclo Celular/antagonistas & inibidores , Inibidores Enzimáticos , Expressão Gênica/efeitos dos fármacos , HIV-1 , Histona Acetiltransferases/antagonistas & inibidores , Terpenos , Fatores de Transcrição/antagonistas & inibidores , Replicação Viral/efeitos dos fármacos , Acetilação , Animais , Fármacos Anti-HIV/síntese química , Fármacos Anti-HIV/química , Fármacos Anti-HIV/farmacologia , Proteínas de Ciclo Celular/genética , Sobrevivência Celular/efeitos dos fármacos , Cromatina/genética , Regulação para Baixo , Inibidores Enzimáticos/síntese química , Inibidores Enzimáticos/química , Inibidores Enzimáticos/farmacologia , HIV-1/efeitos dos fármacos , HIV-1/genética , HIV-1/fisiologia , Células HeLa , Histona Acetiltransferases/genética , Histonas/genética , Humanos , Modelos Moleculares , Estrutura Molecular , Linfócitos T/virologia , Terpenos/síntese química , Terpenos/química , Terpenos/farmacologia , Fatores de Transcrição/genética , Transcrição Gênica , Proteína Supressora de Tumor p53/metabolismo , Regulação para Cima , Fatores de Transcrição de p300-CBPRESUMO
Altered gene expression resulting from changes in the post-translational modification patterns of the histones and DNA is collectively termed epigenetics. Such changes are inherited albeit there are no alterations in the DNA sequence. Epigenetic regulation of gene expression is implemented by a wide repertoire of histone and DNA modifying enzymes including the acetyltransferases and deacetylases, the methyltransferases and kinases among others. Therefore, a regulation of these enzyme activities affords a tighter regulation of gene expression. Conversely, aberrant enzymatic activities lead to unregulated gene expression, resulting in several diseases such as RTS (loss of CBP HAT activity) and Spinal and Bulbar muscular atrophy (HATs and HMTases), apart from several forms of cancers, particularly myeloid leukemia (RAR-PML or RAR-PLZF fusion proteins resulting in the mistargeting of HDACs). Thus these enzymes have emerged as novel targets for the design of therapeutics. In this direction, several small molecule modulators (activators and inhibitors) of HATs, HDACs and HMTases are being reported in literature. This chapter introduces the different histone modifying enzymes involved in gene regulation, their connection to disease manifestation and focuses on the role of small molecule modulators in understanding enzyme function and also the design and the evolution of chromatin therapeutics
Assuntos
Epigênese Genética , Expressão Gênica , Histonas/metabolismo , Processamento de Proteína Pós-Traducional , Acetilação , Animais , DNA (Citosina-5-)-Metiltransferases/metabolismo , Metilação de DNA , Portadores de Fármacos , Inibidores Enzimáticos/administração & dosagem , Inibidores Enzimáticos/farmacologia , Epigênese Genética/efeitos dos fármacos , Expressão Gênica/efeitos dos fármacos , Histona Acetiltransferases/antagonistas & inibidores , Histona Acetiltransferases/metabolismo , Inibidores de Histona Desacetilases , Histona Desacetilases/metabolismo , Histona-Lisina N-Metiltransferase/antagonistas & inibidores , Histona-Lisina N-Metiltransferase/metabolismo , Humanos , Metilação , Neoplasias/genética , Neoplasias/metabolismo , Fosforilação , Protamina Quinase/metabolismo , Processamento de Proteína Pós-Traducional/efeitos dos fármacos , Síndrome de Rubinstein-Taybi/genética , Síndrome de Rubinstein-Taybi/metabolismoRESUMO
Lysine acetyltransferases (KATs), p300 (KAT3B), and its close homologue CREB-binding protein (KAT3A) are probably the most widely studied KATs with well documented roles in various cellular processes. Hence, the dysfunction of p300 may result in the dysregulation of gene expression leading to the manifestation of many disorders. The acetyltransferase activity of p300/CREB-binding protein is therefore considered as a target for new generation therapeutics. We describe here a natural compound, plumbagin (RTK1), isolated from Plumbago rosea root extract, that inhibits histone acetyltransferase activity potently in vivo. Interestingly, RTK1 specifically inhibits the p300-mediated acetylation of p53 but not the acetylation by another acetyltransferase, p300/CREB-binding protein -associated factor, PCAF, in vivo. RTK1 inhibits p300 histone acetyltransferase activity in a noncompetitive manner. Docking studies and site-directed mutagenesis of the p300 histone acetyltransferase domain suggest that a single hydroxyl group of RTK1 makes a hydrogen bond with the lysine 1358 residue of this domain. In agreement with this, we found that indeed the hydroxyl group-substituted plumbagin derivatives lost the acetyltransferase inhibitory activity. This study describes for the first time the chemical entity (hydroxyl group) required for the inhibition of acetyltransferase activity.