A conserved role for the mitochondrial citrate transporter Sea/SLC25A1 in the maintenance of chromosome integrity

Abstract

Histone acetylation plays essential roles in cell cycle progression, DNA repair, gene expression and silencing. Although the knowledge regarding the roles of acetylation of histone lysine residues is rapidly growing, very little is known about the biochemical pathways providing the nucleus with metabolites necessary for physiological chromatin acetylation. Here, we show that mutations in the scheggia (sea)-encoded Sea protein, the Drosophila ortholog of the human mitochondrial citrate carrier Solute carrier 25 A1 (SLC25A1), impair citrate transport from mitochondria to the cytosol. Interestingly, inhibition of sea expression results in extensive chromosome breakage in mitotic cells and induces an ATR-dependent cell cycle arrest associated with a dramatic reduction of global histone acetylation. Notably, loss of SLC25A1 in short interfering RNA (siRNA)-treated human primary fibroblasts also leads to chromosome breaks and histone acetylation defects, suggesting an evolutionary conserved role for Sea/SLC25A1 in the regulation of chromosome integrity. This study therefore provides an intriguing and unexpected link between intermediary metabolism and epigenetic control of genome stability.

Citrate – new functions for an old metabolite

“…Two approaches have been used to identify these new functions. The first is based on the inhibition of mitochondrial CIC activity by the specific substrate analogue 1,2,3-benzene-tricarboxylate (BTA) Infantino et al, 2011a;Cappello et al, 2012;Catalina-Rodriguez et al, 2012) and the second by siRNA gene silencing Morciano et al, 2009;Infantino et al, 2011a;Catalina-Rodriguez et al, 2012). Recently, by mutational analysis of the SLC25A1 gene (Edvardson et al, 2013;Nota et al, 2013), different mutations were identified in patients with agenesis of corpus callosum and hydroxyglutaric aciduria.…”

“…This results in altered histone methylation marks and dysregulated cellular differentiation. Taking into consideration that the CIC gene has previously been implicated in epigenetic and cancer biology (Morciano et al, 2009;Wellen et al, 2009;Catalina-Rodriguez et al, 2012) and that CIC gene defect causes elevation of 2-HG (see section Citrate in Neurodevelopmental Syndromes and Hydroxyglutaric Aciduria), the previous hypothesis needs to be further focused and investigated. It is interesting to note that 2-HG can also increase in the absence of metabolic enzyme mutations.…”

“…However, the acetylation of histones does not depend on ACLY activity but is linked to the cytosolic citrate pool, suggesting that a crucial role is performed by the CIC as a citrate supplier. Morciano et al (2009) demonstrated that mutations in CIC, which impairs transport of citrate from mitochondria, cause a very significant reduction of histone acetylation. Moreover, the use of siRNA reduces CIC gene expression by 70% and leads to chromosome breaks in Drosophila and human primary fibroblasts.…”

“…Moreover, the use of siRNA reduces CIC gene expression by 70% and leads to chromosome breaks in Drosophila and human primary fibroblasts. Such breakage is rescued by treating mutant cells with citrate and TSA, an inhibitor of HDAC (Morciano et al, 2009). …”

Phenotypic analysis of misato function reveals roles of noncentrosomal microtubules in Drosophila spindle formation

“…Mitochondrial extracts were generated as described (Morciano et al, 2009). The quality of the extracts was checked by western blotting using an antibody against the Sea/SLC25A1 mitochondrial marker (Morciano et al, 2009) diluted 1:2000.…”