Alveolar rhabdomyosarcoma-associated proteins PAX3/FOXO1A and PAX7/FOXO1A suppress the transcriptional activity of MyoD-target genes in muscle stem cells
Alveolar rhabdomyosarcoma-associated proteins PAX3/FOXO1A and PAX7/FOXO1A suppress the transcriptional activity of MyoD-target genes in muscle stem cells
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DOI：
10.1038/onc.2012.73
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发表时间：
2013-01-31
期刊：
影响因子：
8
通讯作者：
Zammit, P. S.
中科院分区：
文献类型：
--
作者：
Calhabeu, F.;Hayashi, S.;Zammit, P. S.
横纹肌肉瘤(RMS)是儿童最常见的软组织肉瘤，其特征是表达肌源性蛋白，包括转录因子MyoD和Mygenin。有两个主要的亚型，胚胎型RMS和肺泡型RMS(ARM)。大多数手臂与染色体易位有关，这些易位在PAX3或PAX7以及FOXO1A的内含子中有断裂点。这些易位分别产生了被称为PAX3/FOXO1A和PAX7/FOXO1A的嵌合转录因子。在异位表达PAX3/FOXO1A的小鼠中，与其他基因操作一起，分化成肌细胞和卫星细胞(出生后肌肉的驻留干细胞)都可以产生具有手臂特征的肿瘤。由于PAX3和PAX7是调控子宫内和出生后早期肌肉干细胞功能的转录网络的一部分，PAX3/FOXO1A和PAX7/FOXO1A可能会破坏正常的PAX3和PAX7功能。在这里，我们研究了PAX3/FOXO1A和PAX7/FOXO1A如何影响卫星细胞的肌肉发生。Pax3/FOXO1A或PAX7/FOXO1A抑制NNurine卫星细胞中肌生成素的表达并阻止终末分化：与显性阴性(DN)Pax3或Pax7构建的效果相同。PAX3/FOXO1A或PAX7/FOXO1A可再次抑制C2C12肌源性细胞MyoD靶基因mygenin和肌肉肌酸激酶的转录。Pax3/FOXO1A或PAX7/FOXO1A不能通过干扰MyoD的表达、定位、磷酸化或与E蛋白的相互作用来抑制MyoD的转录活性。染色质免疫沉淀显示PAX3/FOXO1A或PAX7/FOXO1A不能阻止MyoD结合。然而，PAX3/FOXO1A或PAX7/FOXO1A减少了RNA聚合酶II对肌生成素启动子的占据，并减少了组蛋白H4的乙酰化，但不直接与肌生成素启动子结合。综上所述，这些观察表明，PAX3/FOXO1A和PAX7/FOXO1A通过抑制MyoD靶基因的转录激活来阻止肌源性分化。Oncogene(2013年)32,651-662；doi：10.1038/onc.2012.73；2012年6月18日在线发布
Rhabdomyosarcoma (RMS) is the commonest soft-tissue sarcoma in childhood and is characterized by expression of myogenic proteins, including the transcription factors MyoD and myogenin. There are two main subgroups, embryonal RMS and alveolar RMS (ARMS). Most ARMS are associated with chromosomal translocations that have breakpoints in introns of either PAX3 or PAX7, and FOXO1A. These translocations create chimeric transcription factors termed PAX3/FOXO1A and PAX7/FOXO1A respectively. Upon ectopic PAX3/FOXO1A expression, together with other genetic manipulation in mice, both differentiating myoblasts and satellite cells (the resident stem cells of postnatal muscle) can give rise to tumours with ARMS characteristics. As PAX3 and PAX7 are part of transcriptional networks that regulate muscle stem cell function in utero and during early postnatal life, PAX3/FOXO1A and PAX7/FOXO1A may subvert normal PAX3 and PAX7 functions. Here we examined how PAX3/FOXO1A and PAX7/FOXO1A affect myogenesis in satellite cells. PAX3/FOXO1A or PAX7/FOXO1A inhibited myogenin expression and prevented terminal differentiation in nnurine satellite cells: the same effect as dominant-negative (DN) Pax3 or Pax7 constructs. The transcription of MyoD-target genes myogenin and muscle creatine kinase were suppressed by PAX3/FOXO1A or PAX7/FOXO1A in C2C12 myogenic cells again as seen with Pax3/7DN. PAX3/FOXO1A or PAX7/FOXO1A did not inhibit the transcriptional activity of MyoD by perturbing MyoD expression, localization, phosphorylation or interaction with E-proteins. Chromatin immunoprecipitation on the myogenin promoter showed that PAX3/FOXO1A or PAX7/FOXO1A did not prevent MyoD from binding. However, PAX3/FOXO1A or PAX7/FOXO1A reduced occupation of the myogenin promoter by RNA polynnerase II and decreased acetylation of histone H4, but did not directly bind to the myogenin promoter. Together, these observations reveal that PAX3/FOXO1A and PAX7/FOXO1A act to prevent myogenic differentiation via suppression of the transcriptional activation of MyoD-target genes. Oncogene (2013) 32, 651-662; doi:10.1038/onc.2012.73; published online 18 June 2012