pRb is required for MEF2-dependent gene expression as well as cell-cycle arrest during skeletal muscle differentiation
pRb is required for MEF2-dependent gene expression as well as cell-cycle arrest during skeletal muscle differentiation
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DOI：
10.1016/s0960-9822(99)80210-3
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发表时间：
1999-05-06
期刊：
影响因子：
9.2
通讯作者：
Lassar, AB
中科院分区：
文献类型：
--
作者：
Novitch, BG;Spicer, DB;Lassar, AB
背景：骨骼肌中分化特异性基因表达的开始与细胞周期的永久退出相关联。视网膜母细胞瘤肿瘤抑制蛋白（pRb）是这一过程的关键调节因子，是细胞周期停滞在GO期和晚期肌肉分化标志物高水平表达所必需的。虽然在pRb缺陷的肌细胞中观察到的细胞周期缺陷可以通过pRb作为从G1期到S期过渡的负调节剂的良好描述的功能来解释，但仍然不清楚pRb如何积极影响晚期肌肉基因表达。在这里，我们表明Rb-/-细胞中的肌源性缺陷对应于转录因子MEF 2活性的缺陷，没有pRb，MyoD诱导核定位的MEF 2的积累，该MEF 2能够结合DNA但转录惰性。当pRb存在时，MyoD刺激MEF 2C转录激活结构域的功能和内源性MEF 2型因子的活性。MyoD与含有疱疹病毒VP 16转录激活结构域的活化形式的MEF 2C一起共转染部分绕过了对pRb的需求，并诱导复制细胞中的晚期肌肉基因表达。然而，这种异位肌生成显着增强的共表达的E2 F1-pRb嵌合蛋白，阻断细胞cycle.Conclusion：这些研究结果表明，pRb促进晚期肌肉分化标志物的表达，通过抑制细胞周期的进展，并与MyoD合作，以促进MEF 2的转录激活活性。
Background: The onset of differentiation-specific gene expression in skeletal muscle is coupled to permanent withdrawal from the cell cycle. The retinoblastoma tumor-suppressor protein (pRb) is a critical regulator of this process, required for both cell-cycle arrest in GO phase and high-level expression of late muscle-differentiation markers. Although the cell-cycle defects that are seen in pRb-deficient myocytes can be explained by the well-described function of pRb as a negative regulator of the transition from G1 to S phase, it remains unclear how pRb positively affects late muscle-gene expression.Results: Here, we show that the myogenic defect in Rb-/- cells corresponds to a deficiency in the activity of the transcription factor MEF2, Without pRb, MyoD induces the accumulation of nuclear-localized MEF2 that is competent to bind DNA yet transcriptionally inert. When pRb is present, MyoD stimulates the function of the MEF2C transcriptional activation domain and the activity of endogenous MEF2-type factors. Co-transfection of MyoD together with an activated form of MEF2C containing the Herpesvirus VP16 transcriptional activation domain partially bypasses the requirement for pRb and induces late muscle-gene expression in replicating cells. This ectopic myogenesis is nevertheless significantly augmented by co-expression of an E2F1-pRb chimeric protein that blocks the cell cycle.Conclusion: These findings indicate that pRb promotes the expression of late-stage muscle-differentiation markers by both inhibiting cell-cycle progression and cooperating with MyoD to promote the transcriptional activation activity of MEF2.