REGULATION OF RRNA SYNTHESIS DURING CARDIAC HYPERTROPHY

心脏肥大通常发生在新生儿心脏， 心脏，是由各种生理和病理条件引起的 如局部缺血、高血压和甲状腺毒症。 在此过程中 心肌细胞增加的是大小而不是数量。 的 大小的增加与蛋白质的增加率有关 合成. 为了增加细胞蛋白质合成的能力， 细胞通过合成更多的核糖体来增加核糖体的数量。在 这一过程影响核糖体RNA基因（rDNA）的转录速率， 提高了 我们将测量的数额和活动的 rDNA转录系统的组成部分，以确定如何 这些因子在hY肥大过程中受到调节。 分子 和免疫探针将被开发用于分析 在mRNA和蛋白质水平上调节因子的表达 心脏肥大时的水平。 大鼠DNA载体的构建 两种基因中的各种突变，如缺失和取代突变， 已知和推定的rDNA顺式作用调节元件 启动子，如UBF结合位点、SL-1结合位点、CRE，和 AP-1位点，将用于定位顺式作用调控元件 参与调节rDNA转录过程中的细胞 肥厚 这些实验将涉及突变体的共转染， 和假野生型启动子导入培养的新生大鼠心脏 肌细胞 在最初的一系列实验中， 这些顺式作用元件，转染的细胞将暴露于 肥大刺激，如佛波醇酯和毛喉素。 一次 如果确定了具体要素，我们将研究其在 肥大反应表现为自发收缩的细胞， 与KC 1停滞的非收缩细胞相比。 的行为 突变型和假的野生型启动子将通过寡核苷酸 使用从诱导的和非诱导的细胞中分离的RNA进行定向引物延伸 转染细胞 这些实验应该（1）证明rRNA基因是如何被调控的 在心脏肥大和（2）导致实验，将允许 阐明了从细胞内信号传导途径， 启动心脏肥大过程的刺激。

Cardiac hypertrophy occurs normally in neonatal hearts and, in adult hearts, is induced by various physiological and pathological conditions such as ischemia, hypertension, and thyrotoxicosis. During this process the cardiac muscle cells increase is size but not in number. The increase in size is associated with an increased rate of protein synthesis. To increase the cellular capacity for protein synthesis, the cells increase the number of ribosomes by synthesizing more of them. In this process the rate of transcription of the ribosomal RNA genes (rDNA) is increased. We will measure both the amounts and activities of the components of the rDNA transcription system in order to determine how these factors are regulated during the process of hYPertrophy. Molecular and immunological probes will be developed for the analysis of the regulation of expression of the factors at both the mRNA and protein levels during cardiac hypertrophy. Constructs of cloned rat DNA carrying various mutations, such as deletion and substitution mutations, in both the known and putative cis-acting regulatory elements of the rDNA promoter, such as the UBF binding site, the SL-l binding sites, CRE, and AP-1 sites, will be used to map the cis-acting regulatory elements involved in the regulation of rDNA transcription during cellular hypertrophy. These experiments will involve the cotransfection of mutant and pseudo, wild-type promoters into cultured neonatal rat cardiac myocytes. In the initial series of experiments to determine the role of these cis-acting elements, the transfected cells will be exposed to hypertrophic stimuli, such as phorbol ester and forskolin. Once a specific element is identified, we will examine its role in the hypertrophic response exhibited by spontaneously contracting cells in comparison to KC1 arrested, non-contracting cells. The behavior of the mutant and pseudo, wild-type promoters will be assayed by oligonucleotide directed primer extension using RNA isolated from induced and noninduced transfected cells. These experiments should (1) demonstrate how the rRNA genes are regulated during cardiac hypertrophy and (2) lead to experiments that will allow the elucidation of the signal transduction pathway(s) that lead from the initiating stimulus to the process of cardiac hypertrophy.