RESUMO
Although there is a binding site on the proteasome for the polyubiquitin chains attached to degradation substrates by the ubiquitination machinery, it is currently unclear whether in vivo the activities of the ubiquitination machinery and the proteasome are coupled. Here we show that two human homologs of the yeast ubiquitin-like Dsk2 protein, hPLIC-1 and hPLIC-2, physically associate with both proteasomes and ubiquitin ligases in large complexes. Overexpression of hPLIC proteins interferes with the in vivo degradation of two unrelated ubiquitin-dependent proteasome substrates, p53 and IkappaBalpha, but not a ubiquitin-independent substrate. Our findings raise the possibility that the hPLIC proteins, and possibly related ubiquitin-like family members, may functionally link the ubiquitination machinery to the proteasome to affect in vivo protein degradation.
Assuntos
Proteínas de Transporte , Proteínas de Ciclo Celular , Cisteína Endopeptidases/metabolismo , Complexos Multienzimáticos/metabolismo , Proteínas de Saccharomyces cerevisiae , Ubiquitinas/metabolismo , Proteínas Adaptadoras de Transdução de Sinal , Sequência de Aminoácidos , Animais , Proteínas Relacionadas à Autofagia , Células Cultivadas , Proteínas Fúngicas/química , Proteínas Fúngicas/metabolismo , Regulação da Expressão Gênica/efeitos dos fármacos , Humanos , Queratinócitos/citologia , Queratinócitos/metabolismo , Masculino , Camundongos , Dados de Sequência Molecular , Complexo de Endopeptidases do Proteassoma , Proteínas Recombinantes/metabolismo , Saccharomyces cerevisiae/metabolismo , Alinhamento de Sequência , Homologia de Sequência de Aminoácidos , Pele/citologia , Transfecção , Fator de Necrose Tumoral alfa/farmacologia , Ubiquitinas/química , Ubiquitinas/genéticaRESUMO
Histone acetyltransferases (HATs) play important roles in the regulation of gene expression. In this report, we describe the design, synthesis, and application of peptide CoA conjugates as selective HAT inhibitors for the transcriptional coactivators p300 and PCAF. Two inhibitors (Lys-CoA for p300 and H3-CoA-20 for PCAF) were found to be potent (IC(50) approximately = 0.5 microM) and selective (approximately 200-fold) in blocking p300 and PCAF HAT activities. These inhibitors were used to probe enzymatic and transcriptional features of HAT function in several assay systems. These compounds should be broadly useful as biological tools for evaluating the roles of HATs in transcriptional studies and may serve as lead agents for the development of novel antineoplastic therapeutics.
