Abstract Gravitational unloading leads to a slow-to-fast shift in the myosin phenotype. The reason for these changes is a decrease in the expression of the genes encoding heavy chains of myosin (MyHC) of the slow type, and an increase in the expression of the genes encoding MyHC of the fast types. Signal cascades such as calcineurin/NFAT and HDAC4/MEF-2D are known to regulate MyHC I gene expression. There is almost no data in the literature on the content of transcription factors NFATc1 and MEF-2D involved in the regulation of the gene expression of MyHC I, as well as histone deacetylase HDAC4 and MAP kinase ERK2 in the rat soleus muscle under the gravitational unloading. The aim of this study was to explore the role of various mechanisms controlling the expression of MyHC type I at each stage of gravitational unloading. The levels of proteins MEF-2D and ERK2 in the nuclear fraction were decreased significantly after 3 and 7 days of unloading, and the level of NFATc1 was decreased on the first and seventh days. However, the content of NFATc1, HDAC4, MEF-2D and ERK2 in the nuclear fraction after 14 days of gravitational unloading corresponded to the control level. These data indicate that the content of transcriptional regulators in the muscle nuclei at a late stage of gravitational unloading is not a limiting factor for maintaining their transcriptional activity.

中文翻译：

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重力卸载下调节大鼠比目鱼肌中MyHC I(β)表达的转录因子肌核含量的时间进程

摘要重力卸载导致肌球蛋白表型从慢到快转变。这些变化的原因是编码慢型肌球蛋白重链 (MyHC) 的基因表达降低，而编码快型 MyHC 的基因表达增加。已知信号级联如钙调神经磷酸酶/NFAT 和 HDAC4/MEF-2D 可调节 MyHC I 基因表达。文献中几乎没有关于重力卸载下大鼠比目鱼肌中参与调节MyHC I基因表达的转录因子NFATc1和MEF-2D，以及组蛋白去乙酰化酶HDAC4和MAP激酶ERK2的含量的资料。 . 本研究的目的是探索在重力卸载的每个阶段控制 MyHC I 型表达的各种机制的作用。细胞核部分MEF-2D和ERK2蛋白水平在卸载3天和7天后显着下降，NFATc1水平在第1天和第7天下降。然而，在14天的重力卸载后核部分中NFATc1、HDAC4、MEF-2D和ERK2的含量与对照水平相对应。这些数据表明，在重力卸载后期肌肉核中转录调节因子的含量不是维持其转录活性的限制因素。重力卸载 14 天后，核部分中的 MEF-2D 和 ERK2 对应于对照水平。这些数据表明，在重力卸载后期肌肉核中转录调节因子的含量不是维持其转录活性的限制因素。重力卸载 14 天后，核部分中的 MEF-2D 和 ERK2 对应于对照水平。这些数据表明，在重力卸载后期肌肉核中转录调节因子的含量不是维持其转录活性的限制因素。