Nuclear activity of carnitine acetyltransferase

点击翻译按钮获取中文摘要

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 acetylome***2. To determine the sequence and mechanism involved in CrAT nuclear addressing***3. To determine the impact of CrAT on genetic integrity and DNA damage response***Conclusion:***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.