Transcription Programming in Cardiac Growth

描述（由申请人提供）：我们的实验室已经确定了乙酰转移酶p300在产后心肌细胞生长调节中的关键作用。我们发现乙酰转移酶p300在大多数或所有形式的心脏肥厚中迅速上调。我们已经证明p300的细胞浓度与心肌细胞的生长能力直接和化学计量相关，因此即使p300水平的微小变化对心肌细胞的生长也有很大的影响。单个p300等位基因的缺失足以损害心脏随着年龄增长和压力过载的生长。我们还发现p300在缺血和氧化应激期间也被迅速诱导，在那里它传递细胞保护信号。因此，p300的快速诱导似乎是一个关键的心脏应激反应。尽管动态控制p300水平可能很重要，但在压力下控制p300 mRNA和蛋白水平上调的机制尚不清楚。基于这些发现，我们假设：(1)心脏应激期间“即刻-早期”，肌细胞自主诱导p300是其他已知效应物（包括钙调磷酸酶）诱导心脏肥厚的节点事件；(2)p300的诱导是由一系列信号响应的转录前和转录后事件介导的，包括磷酸化、乙酰化、泛素化和非编码rna抑制的去除。我们提议测试乙酰化和磷酸化调节剂的影响，以及特定的p300调节的miRs在肥厚信号传导过程中对p300积累和乙酰转移酶活性的作用。我们将进行心脏特异性p300和CBP的删除，以确定这些蛋白在肥大中是否具有独特的或肌细胞自主的作用。最后，我们将在p300tg与HDAC5或9缺失小鼠之间，以及p300缺失与钙调神经磷酸酶tg小鼠之间进行基因互补实验。这些实验将明确确立p300相对于II类组蛋白去乙酰化酶和钙调磷酸酶在体内肥厚信号转导中的地位。超过300万美国人患有心力衰竭。尽管临床取得了重大进展，但死亡率仍然极高；只有不到40%的患者在首次心力衰竭发作后能存活5年。心脏在衰竭前数月或数年开始肥大或增大。肥厚本身是一个独立的死亡危险因素。目前还没有预防肥厚或延缓其发展为心力衰竭的治疗方法。通过揭示肥厚的特定分子信号，我们的研究可能有助于为这些常见和致命的心脏病提供新的治疗方法。

DESCRIPTION (provided by applicant): Our laboratory has identified a critical role for the acetyltransferase p300 in the regulation of postnatal cardiac myocyte growth. We find that acetyltransferase p300 is rapidly upregulated in most or all forms of cardiac hypertrophy. We have shown that the cellular concentration of p300 is directly and stoichometrically related to cardiac myocyte growth capacity, such that even small changes in p300 levels have large effects on myocyte growth. Loss of a single p300 allele is sufficient to impair cardiac growth with age and in response to pressure overload. We also find that p300 is also rapidly induced during ischemic and oxidative stress, where it conveys a cytoprotective signal. The rapid induction of p300 thus appears to be a critical cardiac stress response. Despite the likely importance of dynamic control of p300 levels, nothing is known about the mechanisms that control upregulation of p300 mRNA and protein levels during stress. Based on these findings, we hypothesize that (1)"immediate-early", myocyte-autonomous induction of p300 during cardiac stress is the nodal event in the induction of cardiac hypertrophy by other identified effectors, including calcineurin, and that (2) induction of p300 is mediated by a sequence of signal-responsive pre- and post- transcriptional events, including phosphorylation, acetylation, ubiquitination, and removal of repression by non-coding RNAs. We propose to test the impact of modulators of acetylation and phosphorylation, and the role of specific p300-regulated miRs, on the accumulation and acetyltransferase activity of p300 during hypertrophic signaling. We will carry out cardiac-specific deletion of p300 and CBP to determine whether these proteins have distinct or myocyte-autonomous roles in hypertrophy. Finally, we will perform genetic complementation experiments between p300tg and HDAC5- or 9-deficient mice, and between p300-deficient and calcineurin tg mice. These experiments will definitively establish the position of p300 relative to the class II histone deacetylases and calcineurin in the transduction of hypertrophic signals in vivo. PUBLIC HEALTH RELEVANCE More than three million Americans are living with heart failure. Despite significant clinical advances, mortality remains extremely high; fewer than 40% will survive 5 years after their first episode of heart failure. The heart begins to undergo hypertrophy, or enlargement, months or years before it fails. Hypertrophy by itself is an independent risk factor for death. No therapy exists to prevent hypertrophy or delay its progression to heart failure. By revealing the specific molecular signals for hypertrophy, our studies may help lead to new treatments for these common and lethal forms of heart disease.