RESUMEN
MicroRNAs and chromatin remodeling complexes represent powerful epigenetic mechanisms that regulate the pluripotent state. miR-302 is a strong inducer of pluripotency, which is characterized by a distinct chromatin architecture. This suggests that miR-302 regulates global chromatin structure; however, a direct relationship between miR-302 and chromatin remodelers has not been established. Here, we provide data to show that miR-302 regulates Brg1 chromatin remodeling complex composition in human embryonic stem cells (hESCs) through direct repression of the BAF53a and BAF170 subunits. With the subsequent overexpression of BAF170 in hESCs, we show that miR-302's inhibition of BAF170 protein levels can affect the expression of genes involved in cell proliferation. Furthermore, miR-302-mediated repression of BAF170 regulates pluripotency by positively influencing mesendodermal differentiation. Overexpression of BAF170 in hESCs led to biased differentiation toward the ectoderm lineage during EB formation and severely hindered directed definitive endoderm differentiation. Taken together, these data uncover a direct regulatory relationship between miR-302 and the Brg1 chromatin remodeling complex that controls gene expression and cell fate decisions in hESCs and suggests that similar mechanisms are at play during early human development.
Asunto(s)
Diferenciación Celular/genética , Ensamble y Desensamble de Cromatina/genética , ADN Helicasas/genética , Células Madre Embrionarias/metabolismo , MicroARNs/genética , Proteínas Nucleares/genética , Factores de Transcripción/genética , Actinas/genética , Actinas/metabolismo , Proliferación Celular/genética , Cromatina/genética , Proteínas Cromosómicas no Histona/genética , Proteínas Cromosómicas no Histona/metabolismo , ADN Helicasas/metabolismo , Proteínas de Unión al ADN/genética , Proteínas de Unión al ADN/metabolismo , Endodermo/crecimiento & desarrollo , Humanos , MicroARNs/metabolismo , Proteínas Nucleares/metabolismo , Células Madre Pluripotentes , Factores de Transcripción/metabolismoRESUMEN
The proteasome has been implicated in transcriptional control in a bewildering number of ways, and many questions remain about how functional selectivity is conferred to its action. Here we discuss transcriptional roles for the ubiquitin receptor Rad23 and posit that such receptors may be key players dictating proteasome transcriptional specificity.
Asunto(s)
Proteínas de Unión al ADN/metabolismo , Complejo de la Endopetidasa Proteasomal/metabolismo , Proteínas de Saccharomyces cerevisiae/metabolismo , Saccharomyces cerevisiae/metabolismo , Transcripción Genética , Ubiquitina/metabolismoRESUMEN
The transcriptional response to damaging agents is of fundamental significance for understanding mechanisms responsible for cell survival and genome maintenance. However, how damage signals are transmitted to the transcriptional apparatus is poorly understood. Here we identify two new regulators of the UV response transcriptome: Snf1, a nutrient-sensing kinase, and Rad23, a nucleotide excision repair factor with no previously known function in transcriptional control. Over half of all UV-responsive genes are dependent on Snf1 or Rad23 for proper regulation. After irradiation, Snf1 targets the Mig3 repressor, a new effector of the UV response. Snf1 and Rad23 are both required for the displacement of Mig3 from the UV-activated HUG1 promoter, and Rad23's activity is functionally linked to the proteasome 19S regulatory particle. Our data reveal overlapping functions for Snf1 and Rad23 in UV-responsive transcriptional regulation and provide mechanistic insight into the action of these factors at a UV-activated promoter. These results also highlight how diverse environmental stimuli are processed by a limited repertoire of signalling molecules to result in tailored patterns of gene expression.
