Regulation Of Histone H4K5 Acetyletion On Saccharomyces.cerevisiae In Respond To Nickel Chloride

Nickel is a heavy metal with high industrial and health risks and is closely related with environmental heavy metal pollution.Long-term exposure to nickel and its compounds can lead to various diseases,such as contact dermatitis,organ system toxicity and cancer.The main factors of cytotoxicity caused by nickel can be attributed to oxidative stress and epigenetic information changes.Nickel can modulate gene expression by directly binding to histones or indirectly changing histone modifications or inducing ROS production.However,the pathogenic mechanism of nickel and its compounds is still unclear.Whether epigenetic information can affect the response of cell to nickel stress by regulating gene expression isn't clear.The histone targeted modification mutant strain H4K5R of Saccharomyces cerevisiae was used as the experimental material in this study.The effects of acetylation of histone H4K5 on oxidative damage,antioxidant capacity,histone acetylation and gene expression under nickel stress were analyzed.The main results can be summarized as follows.1.With the increase of NiCl₂ concentration,cell death rate and intracellular ROS content of the wild-type strain BY4741 increased,and the mitochondrial membrane potential?MMP?decreased significantly.The cell death rate and intracellular ROS content of mutant H4K5R were significantly lower than wild type?P<0.05?.However,the intracellular mitochondrial membrane potential of mutant H4K5R was higher than the wild type and tended to a normal state.It was shown that the extent of oxidative damage under NiCl₂ stress of mutant strains is lower less than that of the wild-type strains.2.With the increase of NiCl₂ concentration,the total acetylation level of histone H4 and the level of acetylation at a single lysine site?H4K5,K12,K16,K91?firstly decreased,then increased in wild-type BY4741.Whereas,that in mutant strains was downward trend.It was shown that the removal of H4K5Ac may affect the H4 acetylation modification under nickel stress in S.cerevisiae.Furthermore,compared with the wild type,the decreased trendency of the H4K16Ac level of the mutant strain was intensified,whearas the decreased trendency of the H4K91Ac level became more slowly.It's shown that the loss of K5 acetylation may promote the reduction of H4K16 acetylation and the retention of K91 acetylation.3.RNA-seq analysis showed that differentially expressed genes?DEGs?between the mutant strain H4K5R and the wild strain BY4741 were enriched in ribosomes pathway and ribosome synthesis pathway.It can be inferred that these DEGs may be regulated by H4K5acetylation modification.After NiCl₂ treatment,the functional of DEGs between the mutant and the wild strain were enriched in mitochondrial function.The response of these genes to nickel stress in the mutant H4K5R was weaker than that in the wild type strain BY4741.KEGG enrichment analysis showed that the DEGs under NiCl₂ stress were enriched in multiple signaling pathways including ribosome,oxidation phosphorylation,thermogenesis,citrate cycle,HIF-1 signaling pathway,starch and sucrose metabolism,etc.It was indicated that these pathways were implied with the process of nickel stress in S.cerevisiae.4.Under NiCl₂ stress,gene expression patterns and gene-gene interactions of MAPK pathway between mutant and wild-type strains were changed.Rho1 and Pkc1 are key genes for locking this pathway and downstream target genes.5.Real-time PCR assay verified that MAPK pathway is activated in both mutant strains and wild yeast cell.However,when the signal was transmitted into the nucleus,an opposite gene expression trend of the Swi4/Swi6 transcription factor between the two strains was observed.The gene expression pattern involved covalent chromatin modification was similar to Swi6.It can be extrapolated that these genes may be associated with the deacetylation of H4K5 site.This result is consistent with the result from RNA-seq analysis.This study was expected to provide a insight into the understanding of nickel ions'cytotoxicity,molecular toxicology,and epigenetic regulation of gene expression.Also,this study offered a guideline for further research on the regulation of histone acetylation responded to heavy metal stress in eukaryotes.