HMGA1 down-regulation is crucial for chromatin composition and a gene expression profile permitting myogenic differentiation.
HMGA1 down-regulation is crucial for chromatin composition and a gene expression profile permitting myogenic differentiation.
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DOI：
10.1186/1471-2121-11-64
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发表时间：
2010-08-11
期刊：
影响因子：
--
通讯作者：
Hock R
中科院分区：
文献类型：
--
作者：
Brocher J;Vogel B;Hock R
高迁移率 A 组 (HMGA) 蛋白通过染色质的结构调节以及启动子/增强子区域上多蛋白复合物的形成来调节基因转录。已发现 HMGA 变体的差异表达对于不同的分化过程很重要，并且表达失调与多种疾病有关。在这里，我们使用稳定过表达 HMGA1a-eGFP 的小鼠 C2C12 成肌细胞和 C2C12 细胞来研究 HMGA1 表达水平失调对细胞分化的影响。我们发现 C2C12 细胞的生肌或成骨程序的诱导导致 HMGA1 立即下调。与野生型 C2C12 细胞相比，稳定过表达 HMGA1a-eGFP 的工程细胞系未能分化为肌管。免疫定位研究表明，持续的 HMGA1a-eGFP 表达可阻止通常伴随分化的肌管形成和染色质重组。 Western Blot 分析表明，HMGA1a-eGFP 水平升高会通过组蛋白 H1 的下调或 MeCP2 的过早表达来影响染色质组成。 RT-PCR 分析进一步表明，持续的 HMGA1a 表达也会影响肌原性基因表达，并导致 MyoD、肌细胞生成素、Igf1、Igf2、Igfbp1-3 等基因下调或转录抑制子 Msx1 上调。有趣的是，siRNA 实验表明，HMGA1a 的敲低是必需的，并且足以重新激活诱导的 HMGA1a 过表达细胞中的生肌程序。我们的数据表明，诱导后 HMGA1 下调是启动 C2C12 细胞生肌程序所必需的。诱导后持续的 HMGA1a 表达可防止关键生肌因子的表达。这可能是由于特定的基因调控和/或对染色质的整体影响。我们的数据进一步证实，改变 HMGA1 水平会影响其他染色质蛋白的表达。因此，HMGA1 能够建立特定的染色质组成。这项工作有助于了解 HMGA1 表达差异如何参与细胞分化过程中的染色质组织，并且可能有助于理解恶性或良性肿瘤中发生的 HMGA1 过度表达的影响。
High mobility group A (HMGA) proteins regulate gene transcription through architectural modulation of chromatin and the formation of multi-protein complexes on promoter/enhancer regions. Differential expression of HMGA variants has been found to be important for distinct differentiation processes and deregulated expression was linked to several disorders. Here we used mouse C2C12 myoblasts and C2C12 cells stably over-expressing HMGA1a-eGFP to study the impact of deregulated HMGA1 expression levels on cellular differentiation. We found that induction of the myogenic or osteogenic program of C2C12 cells caused an immediate down-regulation of HMGA1. In contrast to wild type C2C12 cells, an engineered cell line with stable over-expression of HMGA1a-eGFP failed to differentiate into myotubes. Immunolocalization studies demonstrated that sustained HMGA1a-eGFP expression prevented myotube formation and chromatin reorganization that normally accompanies differentiation. Western Blot analyses showed that elevated HMGA1a-eGFP levels affected chromatin composition through either down-regulation of histone H1 or premature expression of MeCP2. RT-PCR analyses further revealed that sustained HMGA1a expression also affected myogenic gene expression and caused either down-regulation of genes such as MyoD, myogenin, Igf1, Igf2, Igfbp1-3 or up-regulation of the transcriptional repressor Msx1. Interestingly, siRNA experiments demonstrated that knock-down of HMGA1a was required and sufficient to reactivate the myogenic program in induced HMGA1a over-expressing cells. Our data demonstrate that HMGA1 down-regulation after induction is required to initiate the myogenic program in C2C12 cells. Sustained HMGA1a expression after induction prevents expression of key myogenic factors. This may be due to specific gene regulation and/or global effects on chromatin. Our data further corroborate that altered HMGA1 levels influence the expression of other chromatin proteins. Thus, HMGA1 is able to establish a specific chromatin composition. This work contributes to the understanding of how differential HMGA1 expression is involved in chromatin organization during cellular differentiation processes and it may help to comprehend effects of HMGA1 over-expression occurring in malign or benign tumours.
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影响因子：
82.9
作者：
Foti, D;Chiefari, E;Brunetti, A
通讯作者：
Brunetti, A
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11.2
作者：
Fedele, M;Fidanza, V;Fusco, A
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4
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作者：
HASTY, P;BRADLEY, A;KLEIN, WH
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KLEIN, WH