RESUMEN
We report three teenaged Caucasian patients with confluent and reticulated papillomatosis whose presentation was atypical due to the absence of hyperpigmentation and presence of a fine white scale.
Asunto(s)
Papiloma/patología , Neoplasias Cutáneas/patología , Adolescente , Adulto , Femenino , Humanos , MasculinoRESUMEN
Death domain-associated protein (Daxx) is a multi-functional protein that modulates both apoptosis and transcription. Within the nucleus, Daxx is a component of the promyelocytic leukemia protein (PML) nuclear bodies (NBs) and interacts with a number of transcription factors, yet its precise role in transcription remains elusive. To further define the function of Daxx, we have isolated its interacting proteins in the nucleus using epitope-tagged affinity purification and identified X-linked mental retardation and alpha-thalassaemia syndrome protein (ATRX), a putative member of the SNF2 family of ATP-dependent chromatin remodeling proteins that is mutated in several X-linked mental retardation disorders. We show that substantial amounts of endogenous Daxx and ATRX exist in a nuclear complex. Daxx binds to ATRX through its paired amphipathic alpha helices domains. ATRX has ATPase activity that is stimulated by mononucleosomes, and patient mutations in the ATPase domain attenuate this activity. ATRX strongly represses transcription when tethered to a promoter. Daxx does not affect the ATPase activity of ATRX, however, it alleviates its transcription repression activity. In addition, ATRX is found in the PML-NBs, and this localization is mediated by Daxx. These results show that the ATRX.Daxx complex is a novel ATP-dependent chromatin-remodeling complex, with ATRX being the core ATPase subunit and Daxx being the targeting subunit. Moreover, the localization of ATRX to the PML-NBs supports the notion that these structures may play an important role in transcription regulation.
Asunto(s)
Proteínas Portadoras/fisiología , ADN Helicasas , Proteínas de Unión al ADN/fisiología , Péptidos y Proteínas de Señalización Intracelular , Proteínas Nucleares/fisiología , Factores de Transcripción/fisiología , Transcripción Genética , Proteínas Adaptadoras Transductoras de Señales , Adenosina Trifosfatasas/química , Adenosina Trifosfato/química , Secuencia de Aminoácidos , Proteínas Portadoras/química , Línea Celular , Núcleo Celular/metabolismo , Cromatina/metabolismo , Cromatografía en Gel , Proteínas Co-Represoras , ADN/química , Proteínas de Unión al ADN/química , Relación Dosis-Respuesta a Droga , Epítopos/química , Eliminación de Gen , Regulación de la Expresión Génica , Genes Reporteros , Células HeLa , Humanos , Microscopía Fluorescente , Modelos Biológicos , Chaperonas Moleculares , Datos de Secuencia Molecular , Mutación , Proteínas Nucleares/química , Plásmidos/metabolismo , Pruebas de Precipitina , Unión Proteica , Estructura Secundaria de Proteína , Estructura Terciaria de Proteína , Proteínas Recombinantes/química , Factores de Transcripción/química , Proteína Nuclear Ligada al Cromosoma XAsunto(s)
Adenosina Trifosfatasas/aislamiento & purificación , Adenosina Trifosfatasas/metabolismo , Factores de Transcripción/aislamiento & purificación , Factores de Transcripción/metabolismo , Animales , Núcleo Celular/metabolismo , Núcleo Celular/ultraestructura , Cromatografía DEAE-Celulosa/métodos , Cromatografía por Intercambio Iónico , Células HeLa , Humanos , Mamíferos , Nucleosomas/genética , Nucleosomas/fisiologíaRESUMEN
Nucleosomal DNA is arranged in a higher-order structure that presents a barrier to most cellular processes involving protein DNA interactions. The cellular machinery involved in sister chromatid cohesion, the cohesin complex, also requires access to the nucleosomal DNA to perform its function in chromosome segregation. The machineries that provide this accessibility are termed chromatin remodelling factors. Here, we report the isolation of a human ISWI (SNF2h)-containing chromatin remodelling complex that encompasses components of the cohesin and NuRD complexes. We show that the hRAD21 subunit of the cohesin complex directly interacts with the ATPase subunit SNF2h. Mapping of hRAD21, SNF2h and Mi2 binding sites by chromatin immunoprecipitation experiments reveals the specific association of these three proteins with human DNA elements containing Alu sequences. We find a correlation between modification of histone tails and association of the SNF2h/cohesin complex with chromatin. Moreover, we show that the association of the cohesin complex with chromatin can be regulated by the state of DNA methylation. Finally, we present evidence pointing to a role for the ATPase activity of SNF2h in the loading of hRAD21 on chromatin.
