Zinc and DHA have opposing effects on the expression levels of histones H3 and H4 in human neuronal cells

Abstract

Zn and DHA have putative neuroprotective effects and these two essential nutrients are known to interact biochemically. We aimed to identify novel protein candidates that are differentially expressed in human neuronal cell line M17 in response to Zn and DHA that would explain the molecular basis of this interaction. Two-dimensional gel electrophoresis and MS were applied to identify major protein expression changes in the protein lysates of human Ml7 neuronal cells that had been grown in the presence and absence of Zn and DHA. Proteomic findings were further investigated using Western immunoblot and real-time PCR analyses. Four protein spots, which had significant differential expression, were identified and selected for in-gel trypsin digestion followed by matrix-assisted laser desorption ionisation MS analysis. The resultant peptide mass fingerprint for each spot allowed their respective identities to be deduced. Two human histone variants H3 and H4 were identified. Both H3 and H4 were downregulated by Zn in the absence of DHA (Zn effect) and upregulated by DHA (DHA effect) in the presence of Zn (physiological condition). These proteomic findings were further supported by Western immunoblot and real-time PCR analyses using H3-and H4-specific monoclonal antibodies and oligonucleotide primers, respectively. We propose that dietary Zn and DHA cause a global effect on gene expression, which is mediated by histones. Such novel information provides possible clues to the molecular basis of neuroprotection by Zn and DHA that may contribute to the future treatment, prevention and management of neurodegenerative diseases such as Alzheimer's disease.

Effect of Zinc and DHA on Expression Levels and Post-Translational Modifications of Histones H3 and H4 in Human Neuronal Cells

“…In order to investigate the change in the expression levels of the histones, proteomic findings were further investigated using western blot and real-time PCR analyses. Our results have revealed the differential expression of histones, particularly histone H3 and H4 in response to DHA and zinc supplementation (Suphioglu, Sadli et al 2010b). In this study, we reported for the first time that both H3 and H4 were significantly downregulated by zinc in the absence of DHA (zinc effect) and up-regulated following DHA treatment at the physiological zinc level (DHA effect), suggesting the interrelationship between zinc and DHA in neuroprotection, which is mediated by histones (Suphioglu, Sadli et al 2010b).…”

“…1.3.2 Possible mechanism of the effect of zinc and DHA on H3 and H4 expression We observed a significant reduction in both mRNA and protein levels of histones H3 and H4 following zinc treatment suggesting that zinc may inhibit the transcription of histones H3 and H4 in M17 human neuronal cells (Suphioglu, Sadli et al 2010b). Histones H3 and H4 possess multiple metal response elements upstream of their start codon, which indicates the possible involvement of zinc in their transcription.…”

“…Previous studies showed that inhibition of DNA synthesis triggers a concerted repression of histone synthesis, indicating that sustained histone synthesis depends on continued DNA synthesis. We proposed that the termination of H3 and H4 synthesis may possibly be caused by the effect of zinc in inhibiting DNA synthesis (Suphioglu, Sadli et al 2010b). Conversely, DHA was found to upregulate H3 and H4 expression levels and abolished the effect of zinc, suggesting the potential contribution of DHA in increasing DNA synthesis, which result in the increase of histone protein levels.…”

“…Our recent data has shown that histone gene and protein expression were affected by both zinc and DHA. The expression levels of histones H3 and H4, in human neuronal cells, were down-regulated by zinc and up-regulated by DHA (Suphioglu, Sadli et al 2010b), suggesting a possible interaction between the two nutrients. Further investigations into the…”

Epigenetics and Metabolism

“…159 Interestingly, docosahexaenoic acid was also shown to increase expression of H3 and H4 histones in the same cell line. 160 By contrast, palmitate induced HAT activity, and several genes that were modulated by lipotoxicity displayed altered patterns of histone modification in clonal β-cells.…”