RESUMO
Small ubiquitin-like modifier (SUMO) modification has emerged as an important posttranslational control of protein functions. Daxx, a transcriptional corepressor, was reported to repress the transcriptional potential of several transcription factors and target to PML oncogenic domains (PODs) via SUMO-dependent interactions. The mechanism by which Daxx binds to sumoylated factors mediating transcriptional and subnuclear compartmental regulation remains unclear. Here, we define a SUMO-interacting motif (SIM) within Daxx and show it to be crucial for targeting Daxx to PODs and for transrepression of several sumoylated transcription factors, including glucocorticoid receptor (GR). In addition, the capability of Daxx SIM to bind SUMO also controls Daxx sumoylation. We further demonstrate that arsenic trioxide-induced sumoylation of PML correlates with a change of endogenous Daxx partitioning from GR-regulated gene promoter to PODs and a relief of Daxx repression on GR target gene expression. Our results provide mechanistic insights into Daxx in SUMO-dependent transcriptional control and subnuclear compartmentalization.
Assuntos
Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Proteínas de Transporte/metabolismo , Núcleo Celular/metabolismo , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Proteínas Nucleares/metabolismo , Proteínas Repressoras/metabolismo , Proteínas Modificadoras Pequenas Relacionadas à Ubiquitina/metabolismo , Proteínas Adaptadoras de Transdução de Sinal/química , Motivos de Aminoácidos , Sequência de Aminoácidos , Animais , Trióxido de Arsênio , Arsenicais/farmacologia , Células COS , Proteínas de Transporte/química , Chlorocebus aethiops , Proteínas Correpressoras , Dexametasona/farmacologia , Células HeLa , Humanos , Peptídeos e Proteínas de Sinalização Intracelular/química , Camundongos , Chaperonas Moleculares , Dados de Sequência Molecular , Proteínas de Neoplasias/metabolismo , Proteínas Nucleares/química , Óxidos/farmacologia , Proteína da Leucemia Promielocítica , Ligação Proteica , Estrutura Terciária de Proteína , Transporte Proteico , Receptores de Glucocorticoides/metabolismo , Fatores de Transcrição/metabolismo , Transcrição Gênica/efeitos dos fármacos , Proteínas Supressoras de Tumor/metabolismoRESUMO
The transcriptional activity of the androgen receptor (AR) modulated by positive or negative regulators plays a critical role in controlling the growth and survival of prostate cancer cells. Although numerous positive regulators have been identified, negative regulators of AR are less well understood. We report here that Daxx functions as a negative AR coregulator through direct protein-protein interactions. Overexpression of Daxx suppressed AR-mediated promoter activity in COS-1 and LNCaP cells and AR-mediated prostate-specific antigen expression in LNCaP cells. Conversely, downregulation of endogenous Daxx expression by RNA interference enhances androgen-induced prostate-specific antigen expression in LNCaP cells. In vitro and in vivo interaction studies revealed that Daxx binds to both the amino-terminal and the DNA-binding domain of the AR. Daxx proteins interfere with the AR DNA-binding activity both in vitro and in vivo. Moreover, sumoylation of AR at its amino-terminal domain is involved in Daxx interaction and trans-repression. Together, these findings not only provide a novel role of Daxx in controlling AR transactivation activity but also uncover the mechanism underlying sumoylation-dependent transcriptional repression of the AR.