Post-transcriptional mechanisms of gene regulation in cardiac cell growth and development

 描述(申请人提供)：对于许多基因，稳定状态的信使核糖核酸水平不能准确地反映它们被翻译成蛋白质的程度。在心肌肥厚过程中，影响单个mRNAs翻译的因素还知之甚少。我们的目的是确定胞浆Polya结合蛋白C1(PABPC1)作为一种新的心肌肥厚调节因子的功能。PABPC1选择性地与大多数真核生物mRNAs的3‘-聚(A)尾序列结合，对其整体翻译和翻转起关键作用。我们证明，在出生后心脏发育过程中，小鼠和人类的PABPC1蛋白水平在转录后受到抑制。重要的是，PABPC1蛋白水平在心肌肥厚过程中增加，我们发现PABPC1缺失的小鼠心肌细胞对病理性肥厚具有抵抗力。为了直接检测PABPC1在心肌肥大中的作用，我们建立了四环素诱导的心脏特异性PABPC1转基因小鼠模型。此外，我们还证明，在心脏发育过程中，Pabpc1mRNAs的Poly(A)尾长减少，这与其与多聚体的关联减少和翻译不良是一致的。更重要的是，我们在小鼠和人类的成人心脏中发现了其他稳定的、不同的、含有mRNAs的短聚(A)尾巴。该建议的具体目的是：(1)确定控制PABPC1细胞类型特异性表达的机制(S)；(2)确定PABPC1在心肌细胞肥大生长中的需求；(3)确定PABPC1在调控其靶向mRNA的聚(A)尾长和翻译控制中的作用。我们将结合使用分子、生化、转基因和高通量测序方法来解决这些重要问题。 公共卫生相关性：这项提议将建立一种新的基因调控机制，该机制基于聚(A)尾长的调控变化，影响心脏mRNAs子集的翻译效率。该项目还将剖析聚(A)结合蛋白在刺激心肌肥大中的功能作用，心肌肥厚是一种与许多心脏病有关的疾病。这项拟议中的研究的成功完成将产生对一种未知的基因调节机制的详细了解，并将为治疗影响数百万美国人的心肌肥厚及其相关病理开辟令人兴奋的新治疗机会。

 DESCRIPTION (provided by applicant): For many genes, steady state mRNA levels provide an inaccurate reflection of the extent to which they are translated into proteins. The factors influencing the translation of individual mRNAs during cardiac hypertrophy are poorly understood. Our objective is to determine the function of the cytosolic polyA-binding protein C1 (PABPC1) as a novel regulator of cardiac hypertrophy. PABPC1 selectively binds to the 3'- poly(A) tail sequence of most eukaryotic mRNAs and is critical for their overall translation and turnover. We demonstrate that PABPC1 protein levels in mice and humans are post-transcriptionally suppressed during postnatal heart development. Importantly, PABPC1 protein levels increase during cardiac hypertrophy, and we show that PABPC1 depleted mouse cardiac myocytes are resistant to pathologic hypertrophy. To directly test the role of PABPC1 in cardiac hypertrophy, we have developed a tetracycline-inducible and cardiac-specific PABPC1 transgenic mouse model. Further, we demonstrate that the poly(A) tail length of Pabpc1 mRNAs decreases during heart development, which is consistent with its reduced association with polysomes and poor translation. More significantly, we have discovered other stable, distinct, populations of short poly(A) tail containing mRNAs in adult hearts of mice and humans. The Specific Aims of this proposal are to: (1) Identify mechanism(s) that control cell-type specific expression of PABPC1; (2) Determine the requirement of PABPC1 in hypertrophic growth of cardiac cells; and (3) Determine the role of PABPC1 in modulating the poly(A) tail length and translation control of its target mRNAs in heart. We will use a combination of molecular, biochemical, transgenic and high-throughput sequencing approaches to address these important questions. PUBLIC HEALTH RELVANCE: This proposal will establish a new gene regulatory mechanism based on regulated changes in poly(A) tail length influencing the efficiency with which subset of cardiac mRNAs are translated. This project will also dissect the functional role of a poly(A) binding protein in stimulation of cardiac hypertrophy, a condition that is involved in number of heart diseases. Successful completion of the proposed research will produce detailed understanding of an unexplored mechanism of gene regulation and will open exciting new therapeutic opportunities to treat cardiac hypertrophy and its associated pathologies that affect millions of Americans.