Regulation of CFTR gene expression

囊性纤维化（CF）是一种常染色体隐性遗传病，由功能失调的囊性纤维化跨膜传导调节因子（CFTR）基因产物引起。CFTR基因（CFTR）受启动子序列调控，启动子序列引起低水平的组织特异性基因转录。本提案的总体目标是确定CFTR直接转录的机制，以了解CFTR转录如何与CF的病理生理相关。核小体内核心组蛋白的乙酰化与“开放”染色质的形成有关，这是转录激活所必需的。此外，组蛋白去乙酰化与抑制性或“封闭”的染色质结构有关。在体内，染色质的改变对基因转录的控制至关重要。我们已经证明CFTR转录与组蛋白乙酰转移酶（HAT）和组蛋白去乙酰化酶（HDAC）活性直接相关，但尚不清楚组蛋白乙酰化如何调节CFTR转录。我们认为组蛋白乙酰化直接影响CFTR的转录。目前，指导组蛋白乙酰化到特定基因和调节基因转录的机制尚不清楚。首先，我们希望验证体内CFTR转录调控是通过组蛋白乙酰化介导的假设。基于我们之前的工作，我们将研究转录因子ATF1和CBF/NF-Y以及组蛋白乙酰转移酶辅激活蛋白、p300/ creb结合蛋白（p300/CBP）和p300/CBP相关因子（PCAF）是否介导CFTR的组蛋白乙酰化。我们将确定组蛋白乙酰化在CFTR转录调控中的作用。当CFTR启动子在体内含有一个倒置的CCAAT （Y-box）元件时，CFTR是组蛋白乙酰化的靶标。CFTR转录启动和camp介导的CFTR转录调控都需要Y-box元件，这表明该元件通过与特定转录因子的相互作用，可能对CFTR中染色质的修饰至关重要。其次，我们将验证CCAAT位移蛋白（CDP）在体内将hdac招募到CFTR并受乙酰化调节的假设。CDP是CFTR转录抑制的关键反式调节因子，与由特定HDAC活性组成的共抑制复合物直接相关。CDP与共激活剂p300/CBP相互作用。此外，CDP还受p300/CBP和PCAF的乙酰转移酶（FAT）活性的调节。我们计划测试CDP作为乙酰转移酶和去乙酰化酶功能的底物的作用，并确定CDP的乙酰化是否影响CFTR的转录。

Cystic fibrosis (CF), an autosomal recessive disorder, is caused by a dysfunctional cystic fibrosis transmembrane conductance regulator (CFTR) gene product. The CFTR gene (CFTR) is regulated by promoter sequences that give rise to low levels of tissue-specific gene transcription. The overall objective of this proposal is to determine the mechanisms that direct transcription of CFTR to learn how CFTR transcription is related to the pathophysiology of CF. The acetylation of core histones within the nucleosome is associated with the formation of "open" chromatin, necessary for transcriptional activation. Furthermore, histone deacetylation is associated with repressive, or "closed", chromatin structure. The alteration in chromatin is critical for the control of gene transcription in vivo. We have demonstrated that CFTR transcription is directly associated with histone acetyltransferase (HAT) and histone deacetylase (HDAC) activity, but it is unclear how histone acetylation regulates CFTR transcription. We propose that histone acetylation direct the transcription of CFTR. Currently, the mechanisms that direct histone acetylation to a specific gene and that regulate gene transcription are not well understood. First, we wish to test the hypotheses that regulation of CFTR transcription in vivo is mediated through histone acetylation. Based on our previous work we will examine whether transcription factors ATF1 and CBF/NF-Y and the histone acetyltransferase coactivator proteins, p300/CREB-binding protein (p300/CBP) and p300/CBP-associated factor (PCAF) mediate histone acetylation of CFTR. We will determine the function of histone acetylation in the regulation of CFTR transcription. CFTR is a target of histone acetylation when the CFTR promoter contains an inverted CCAAT (Y-box) element in vivo. Both CFTR transcript initiation and cAMP-mediated CFTR transcription regulation require the Y-box element, suggesting that this element, by interacting with specific transcription factors, may be essential to the modification of chromatin in CFTR. Second, we will test the hypothesis that CCAAT displacement protein (CDP) recruits HDACs to CFTR in vivo and is regulated by acetylation. CDP, a critical trans-acting regulator of CFTR transcriptional repression, is directly associated with a co-repressor complex composed of specific HDAC activity. CDP interacts with the co-activator p300/CBP. Furthermore, CDP is regulated by acetyltransferase (FAT) activities of p300/CBP and PCAF. We plan to test the role of CDP as a substrate for acetyltransferase and deacetylase function and to determine whether the acetylation of CDP effect transcription of CFTR.