Overexpression of the transcription factor UBF1 is sufficient to increase ribosomal DNA transcription in neonatal cardiomyocytes: Implications for cardiac hypertrophy
Overexpression of the transcription factor UBF1 is sufficient to increase ribosomal DNA transcription in neonatal cardiomyocytes: Implications for cardiac hypertrophy
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DOI：
10.1073/pnas.93.16.8750
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发表时间：
1996-08-06
影响因子：
11.1
通讯作者：
Rothblum, LI
中科院分区：
文献类型：
--
作者：
Hannan, RD;Stefanovsky, V;Rothblum, LI
心肌细胞肥大的蛋白质加速积累特征是细胞蛋白质合成能力增加(核糖体含量升高)的结果。核糖体积累的限速步骤是rRNA基因的转录。在去甲肾上腺素或自发收缩诱导的新生心肌细胞肥大过程中，核糖体DNA转录因子UBF的表达变化与核糖体生物发生速率的增加有关。我们假设UBF的高表达是这些肥大刺激影响rDNA启动子转录速率的机制之一。在本研究中，我们直接检测了UBF过表达对培养的新生心肌细胞rDNA转录的影响，在对照实验中，一种新的rDNA转录报告结构(PSMECAT)显示出与肥大刺激(10(-4)M苯肾上腺素、10(-7)M内皮素和自发收缩)类似的活性增加。当收缩停滞的心肌细胞与pSMECAT共转染并增加UBF1表达载体的量时，观察到rDNA转录呈剂量依赖性(3-5倍)增加，Western印迹分析证实过表达的标记UBF聚集在心肌细胞核中。UBF1的过度表达足以增加新生心肌细胞的rDNA转录，这为UBF的调节是与心肌细胞肥大相关的核糖体生物合成和蛋白质积累增加的关键成分提供了证据。
The accelerated protein accumulation characteristic of cardiomyocyte hypertrophy results from increased cellular protein synthetic capacity (elevated ribosome content). The rate limiting step in ribosome accumulation is transcription of the rRNA genes. During neonatal cardiomyocyte hypertrophy induced by norepinephrine or spontaneous contraction, changes in the expression of a ribosomal DNA transcription factor, UBF, correlated with increased rates of ribosome biogenesis. We hypothesized that elevated expression of UBF was part of the mechanism by which these hypertrophic stimuli effected increases in the rate of transcription from the rDNA promoter, In this study, we have examined directly the effect of overexpressing UBF on rDNA transcription in neonatal cardiomyocytes in culture, In control experiments, a novel reporter construct for rDNA transcription (pSMECAT) showed similar increases in activity in response to hypertrophic stimuli (10(-4) M phenylephrine, 10(-7) M endothelin, and spontaneous contraction) as did the endogenous rRNA genes. When contraction-arrested cardiomyocytes were cotransfected with pSMECAT and increasing amounts of a UBF1 expression vector; a dose-dependent (3-5 fold) increase in rDNA transcription was observed, Western blot analysis confirmed that the overexpressed, FLAG-tagged UBF accumulated in the cardiomyocyte nuclei. The observation that overexpression of UBF1 is sufficient to increase rDNA transcription in neonatal cardiomyocytes provides evidence in support of the hypothesis that the regulation of UBF is a key component of the increased ribosome biogenesis and protein accumulation associated with cardiomyocyte hypertrophy.