RESUMEN
p300 and CREB binding protein can both activate and repress transcription. Here, we locate the CRD1 transcriptional repression domain between residues 1017 and 1029 of p300. This region contains two copies of the sequence psiKxE that are modified by the ubiquitin-like protein SUMO-1. Mutations that reduce SUMO modification increase p300-mediated transcriptional activity and expression of a SUMO-specific protease or catalytically inactive Ubc9 relieved repression, demonstrating that p300 repression was mediated by SUMO conjugation. SUMO-modified CRD1 domain bound HDAC6 in vitro, and p300 repression was relieved by histone deacetylase inhibition and siRNA-mediated ablation of HDAC6 expression. These results reveal a mechanism controlling p300 function and suggest that SUMO-dependent repression is mediated by recruitment of HDAC6.
Asunto(s)
Células Eucariotas/metabolismo , Genes Reguladores/genética , Proteínas Nucleares/metabolismo , Proteínas Represoras/metabolismo , Proteína SUMO-1/metabolismo , Transactivadores/metabolismo , Enzimas Ubiquitina-Conjugadoras , Secuencia de Aminoácidos/genética , Sitios de Unión/genética , Estructuras del Núcleo Celular/genética , Estructuras del Núcleo Celular/metabolismo , Proteínas de Unión al ADN/genética , Proteínas de Unión al ADN/metabolismo , Inhibidores Enzimáticos/farmacología , Células HeLa , Histona Desacetilasa 6 , Inhibidores de Histona Desacetilasas , Histona Desacetilasas/genética , Histona Desacetilasas/metabolismo , Humanos , Ligasas/genética , Ligasas/metabolismo , Mutación/genética , Proteínas Nucleares/genética , Estructura Terciaria de Proteína/genética , ARN Interferente Pequeño , Proteínas Represoras/genética , Proteína SUMO-1/genética , Transactivadores/genética , Factores de Transcripción/genética , Factores de Transcripción/metabolismoRESUMEN
The ETS domain transcription factor Elk-1 serves as an integration point for different mitogen-activated protein (MAP) kinase pathways. Phosphorylation of Elk-1 by MAP kinases triggers its activation. However, while the activation process is well understood, its downregulation-inactivation is less well characterized. The ETS DNA-binding domain plays a role in the downregulation of Elk-dependent promoter activity following mitogenic activation by recruiting the mSin3A-HDAC complex. Here we have identified a novel evolutionarily conserved repression domain in Elk-1, termed the R motif, which serves to reduce the basal transcriptional activity of Elk-1 and dampen its response to mitogenic signals. This domain is highly potent and portable and can repress transcription in trans. The R motif is related to the CRD1 repression domain in p300 and can functionally replace this domain and confer p21(waf1/cip1) inducibility on p300. However, the R motif acts in a context-dependent manner and is not p21(waf1/cip1) responsive in Elk-1. Thus, the Elk-1 R motif and the p300 CRD1 motif represent a new class of repression domains that are regulated in a context-dependent manner.