RESUMO
Induction of pluripotency in differentiated cells through the exogenous expression of the transcription factors Oct4, Sox2, Klf4 and cellular Myc involves reprogramming at the epigenetic level. Histones and their metabolism governed by histone chaperones constitute an important regulator of epigenetic control. We hypothesized that histone chaperones facilitate or inhibit the course of reprogramming. For the first time, we report here that the downregulation of histone chaperone Aprataxin PNK-like factor (APLF) promotes reprogramming by augmenting the expression of E-cadherin (Cdh1), which is implicated in the mesenchymal-to-epithelial transition (MET) involved in the generation of induced pluripotent stem cells (iPSCs) from mouse embryonic fibroblasts (MEFs). Downregulation of APLF in MEFs expedites the loss of the repressive MacroH2A.1 (encoded by H2afy) histone variant from the Cdh1 promoter and enhances the incorporation of active histone H3me2K4 marks at the promoters of the pluripotency genes Nanog and Klf4, thereby accelerating the process of cellular reprogramming and increasing the efficiency of iPSC generation. We demonstrate a new histone chaperone (APLF)-MET-histone modification cohort that functions in the induction of pluripotency in fibroblasts. This regulatory axis might provide new mechanistic insights into perspectives of epigenetic regulation involved in cancer metastasis.
Assuntos
Proteínas de Transporte/metabolismo , Fibroblastos/metabolismo , Chaperonas de Histonas/metabolismo , Células-Tronco Pluripotentes Induzidas/metabolismo , Animais , Caderinas/genética , Caderinas/metabolismo , Pontos de Checagem do Ciclo Celular/genética , Diferenciação Celular/genética , Reprogramação Celular/genética , Ensaio de Unidades Formadoras de Colônias , Reparo do DNA/genética , DNA Liase (Sítios Apurínicos ou Apirimidínicos) , Regulação para Baixo/genética , Embrião de Mamíferos/citologia , Células Epiteliais/citologia , Feminino , Fibroblastos/citologia , Técnicas de Silenciamento de Genes , Células HEK293 , Histonas/metabolismo , Humanos , Células-Tronco Pluripotentes Induzidas/citologia , Fator 4 Semelhante a Kruppel , Lisina/metabolismo , Masculino , Mesoderma/citologia , Metilação , Camundongos , Camundongos Endogâmicos C57BL , Proteínas de Ligação a Poli-ADP-Ribose , Regiões Promotoras Genéticas/genética , Regulação para Cima/genéticaRESUMO
RUNX1 (Runt-related transcription factor 1) is indispensable for the generation of hemogenic endothelium. However, the regulation of RUNX1 during this developmental process is poorly understood. We investigated the role of the histone chaperone HIRA (histone cell cycle regulation-defective homolog A) from this perspective and report that HIRA significantly contributes toward the regulation of RUNX1 in the transition of differentiating mouse embryonic stem cells from hemogenic to hematopoietic stage. Direct interaction of HIRA and RUNX1 activates the downstream targets of RUNX1 implicated in generation of hematopoietic stem cells. At the molecular level, HIRA-mediated incorporation of histone H3.3 variant within the Runx1 +24 mouse conserved noncoding element is essential for the expression of Runx1 during endothelial to hematopoietic transition. An inactive chromatin at the intronic enhancer of Runx1 in absence of HIRA significantly repressed the transition of cells from hemogenic to hematopoietic fate. We expect that the HIRA-RUNX1 axis might open up a novel approach in understanding leukemogenesis in future.