Nuclear activity of carnitine acetyltransferase

导语：乙酰辅酶a是核-线粒体串扰的重要介质，令人信服的证据表明，这种中心代谢物的可用性是细胞生长和增殖的关键调节剂，通过调节特定的蛋白质乙酰化反应，特别是在染色质组蛋白上的反应。在我们对精子染色质重塑的研究过程中，我们观察到组蛋白的短暂超乙酰化与其从染色质中移除有关。然而，在这些步骤中，对组蛋白相关蛋白的系统质谱分析没有发现潜在的组蛋白乙酰转移酶候选物。然而，我们观察到线粒体肉碱乙酰转移酶（CrAT）在小鼠和人的线粒体或过氧体中几乎完全的核位移。肉毒碱乙酰转移酶（CrAT），催化乙酰辅酶a自由可逆转化为其膜渗透肉毒碱酯，乙酰肉毒碱。来自人类生殖细胞的RNA分析揭示了剪接变异，其中一个包括部分内含子的保留，该内含子引入了一个早期帧内停止密码子，迫使下游ATG转录，并编码一个缺乏线粒体定位信号的蛋白质，由于存在退化的核定位信号（NLS），可能具有核定位的潜力。转染实验表明，如果c端过氧化物酶体靶向序列（PTS）受阻，该变体可以定位到细胞核。因此，CrAT的核定位可能会改变这个隔室中的乙酰辅酶a池，从而允许在细胞核中进行酶或非酶乙酰化过程。在体细胞中，通过CrAT活性改变核乙酰辅酶a可能对遗传稳定性、诱变和衰老产生重要影响。假设：CrAT的核寻址通过组蛋白和其他核蛋白的乙酰化影响染色质稳定性。目的：我们的目标是研究CrAT的核寻址调控，并初步了解其生物学作用。因此，今后五年的具体目标是：目的：探讨CrAT核表达对染色质和乙酰化酶2的影响。确定CrAT核寻址的顺序和机制。结论：这些实验步骤是我们研究计划的一部分，将确定核CrAT的功能，特别是它是否参与染色质动力学和遗传稳定性。了解线粒体-核串扰是神经退行性疾病、衰老和癌症的合理干预方法的关键。这将为HQP的培训提供一个刺激的研究环境。

Introduction:Acetyl-CoA emerges as one important mediator of the nuclear-mitochondrial crosstalk and compelling evidence indicates that availability of this central metabolite is a key regulator of cell growth and proliferation through modulation of particular protein acetylation reactions, especially those at histones in chromatin. During the course of our investigation on the chromatin remodelling in spermatids, we observed a transient hyperacetylation of histones associated with their eviction from the chromatin. However, a systematic mass spectrometry analysis of histone-associated proteins yielded no potential histone acetyltransferase candidate at these steps. However, we observed a near complete nuclear displacement of the mitochondrial carnitine acetyltransferase (CrAT) normally found in the mitochondria or peroxysomes in both mouse and human. Carnitine acetyltransferase (CrAT), catalyzes the freely reversible conversion of acetyl-CoA to its membrane permeant carnitine ester, acetylcarnitine. RNA analyses from human germ cells revealed splicing variants, one of which included retention of a partial intron that introduces an early in-frame stop codon forcing transcription from a downstream ATG and encoding a protein lacking the mitochondrial localisation signal that may have the potential for nuclear localisation owing for the presence of a degenerated nuclear localisation signal (NLS). Transfection experiments indicate that this variant can localize to the nucleus if the C-terminal peroxisomal targeting sequence (PTS) is hindered. The nuclear localization of CrAT may therefore modify the acetyl-CoA pool in this compartment allowing either enzymatic or non-enzymatic acetylation processes in the nucleus. In somatic cells, alteration of nuclear acetyl-CoA through the CrAT activity may have important consequences on genetic stability, mutagenesis and aging.Hypothesis:The nuclear addressing of CrAT impacts chromatin stability through acetylation of histones and other nuclear proteins.Objectives:Our goal is to investigate regulation of the nuclear addressing of CrAT and get the first insights into its biological role. Accordingly, the specific objectives for the next five years are:1. To determine the consequence of CrAT nuclear expression on chromatin and acetylome2. To determine the sequence and mechanism involved in CrAT nuclear addressing3. To determine the impact of CrAT on genetic integrity and DNA damage responseConclusion:These experimental steps are part of our research program and will define the function of nuclear CrAT, in particular, whether it is involved in chromatin dynamics and genetic stability. Understanding the mitochondrial-nucleus crosstalk is key for rational intervention approaches in neurodegenerative disorders, aging and cancers. This will provide a stimulating research environment for the training of HQP.