Previously uncharacterized amino acid residues in histone H3 and H4 mutants with roles in DNA damage repair response and cellular aging

β-Glucan Enhances the Biocontrol Efficacy of Marine Yeast Scheffersomyeces spartinae W9 against Botrytis cinerea in Strawberries

The marine yeast Scheffersomyeces spartinae W9 is a promising biocontrol agent for gray mold caused by Botrytis cinerea in strawberries. Improving the biocontrol efficacy of S. spartinae W9 is necessary for its commercial application. In this study, different concentrations of β-glucan were added to the culture medium to evaluate its effect on the biocontrol efficacy of S. spartinae W9. The results showed that 0.1% β-glucan could increase the biocontrol effect of S. spartinae W9 against B. cinerea in strawberries and in vitro. We found that adding 0.1% β-glucan to the culture medium promoted the growth of S. spartinae W9 in wounds of strawberries, enhanced biofilm formation ability, and secreted more β-1,3-glucanase. In addition, 0.1% β-glucan increased the survival rate of S. spartinae W9 under oxidative, thermal, osmotic, and plasma membrane stressors. Transcriptome analysis revealed 188 differential expressed genes in S. spartinae W9 cultured with or without 0.1% β-glucan, including 120 upregulated and 68 downregulated genes. The upregulated genes were associated with stress response, cell wall formation, energy production, growth, and reproduction. Thus, culturing with 0.1% β-glucan is an effective way to improve the biocontrol ability of S. spartinae W9 against gray mold in strawberries.

Sub-chronic exposure to PhIP induces oxidative damage and DNA damage, and disrupts the amino acid metabolism in the colons of Wistar rats

Heterocyclic amines (HCAs) are a group of mutagenic compounds produced during thermal processing of protein-rich foods. One of the most abundant HCAs, 2-amino-1-methyl-6-phenylimidazo[4,5-b] pyridine (PhIP) has potential carcinogenic and mutagenic effects on human organs, especially the colon. This study aimed to explore the toxic effects of PhIP on amino acid metabolism in the colon of Wistar rats using RNA-seq and LC-MS/MS. Exposure to PhIP for 4 weeks induced oxidative damage and DNA damage in the colons, and disrupted the expression of related genes involved in tryptophan metabolism, beta(β)-alanine metabolism, valine, leucine, and isoleucine degradation, and glutathione metabolic pathways. Moreover, the levels of fecal metabolites related to amino acid metabolism were affected by PhIP. Cumulatively, these results indicate that PhIP can induce colonic oxidative injury and disorders related to amino acid metabolism, thereby providing a new theoretical basis for the study of PhIP toxicity.

Substitution of histone H3 arginine 72 to alanine leads to deregulation of isoleucine biosynthesis in budding yeast Saccharomyces cerevisiae

Histone residues play an essential role in the regulation of various biological processes. In the present study, we have utilized the H3/H4 histone mutant library to probe functional aspects of histone residues in amino acid biosynthesis. We found that histone residue H3R72 plays a crucial role in the regulation of isoleucine biosynthesis. Substitution of arginine residue (H3R72) of histone H3 to alanine (H3R72A) renders yeast cells unable to grow in the minimal media. Histone mutant H3R72A requires the external supplementation of either isoleucine, serine, or threonine for the growth in minimal media. We also observed that H3R72 residue and leucine amino acid in synthetic complete media might play a crucial role in determining the intake of isoleucine and threonine in yeast. Further, gene deletion analysis of ILV1 and CHA1 in H3R72A mutant confirmed that isoleucine is the sole requirement for growth in minimal medium. Altogether, we have identified that histone H3R72 residue may be crucial for yeast growth in the minimal medium by regulating isoleucine biosynthesis through the Ilv1 enzyme in budding yeast Saccharomyces cerevisiae.

Role of H3K18ac-regulated nucleotide excision repair-related genes in arsenic-induced DNA damage and repair of HaCaT cells

Arsenic is an environmental poison and is a grade I human carcinogen that can cause many types of damage to the body. The skin is one of the main target organs of arsenic damage, but the molecular mechanisms underlying arsenic poisoning are not clear. Arsenic is an epigenetic agent. Histone acetylation is one of the earliest covalent modifications to be discovered and is closely related to the occurrence and development of tumors. To investigate the role of acetylated histone H3K18 (H3K18 ac) in arsenic-induced DNA damage, HaCaT cells were exposed to sodium arsenite (NaAsO₂) for 24 h. It was found that arsenic induced the downregulation of xeroderma pigmentosum A, D, and F (XPA, XPD, and XPF-nucleotide excision repair (NER)-related genes) expression, as well as histone H3K18 ac expression, and aggravated DNA damage. Chromatin immunoprecipitation quantitative polymerase chain reaction (ChIP-qPCR) analysis showed that H3K18 acetylation in the promoter regions of XPA, XPD, and XPF was downregulated. In addition, the use of the histone deacetylase inhibitor trichostatin A (TSA) partially inhibited arsenic-induced DNA damage, inhibited deacetylation of H3K18 ac in the promoter regions of XPA, XPD, and XPF genes, increased acetylation of H3K18, and promoted the transcriptional expression of NER-related genes. Our study revealed that NaAsO₂ induces DNA damage and inhibits the expression of NER-related genes, while TSA increases the H3K18 ac enrichment level and promotes the transcriptional expression of NER, thereby inhibiting DNA damage. These findings provide new ideas for understanding the molecular mechanisms underlying arsenic-induced skin damage.

Identification of Histone H3 and H4 Amino Acid Residues Important for the Regulation of Arsenite Stress Signaling in Saccharomyces cerevisiae

Arsenic is an environmental carcinogen that causes many diseases in humans, including cancers and organ failures, affecting millions of people in the world. Arsenic trioxide is a drug used for the treatment of acute promyelocytic leukemia (APL). In the present study, we screened the synthetic histone H3 and H4 library in the presence of arsenite to understand the role of histone residues in arsenic toxicity. We identified residues of histone H3 and H4 crucial for arsenite stress response. The residues H3T3, H3G90, H4K5, H4G13, and H4R95 are required for the activation of Hog1 kinase in response to arsenite exposure. We showed that a reduced level of Hog1 activation increases the intracellular arsenic content in these histone mutants through the Fps1 channel. We have also noticed the reduced expression of ACR3 exporter in the mutants. The growth defect of mutants caused by arsenite exposure was suppressed in hyperosmotic conditions, in a higher concentration of glucose, and upon deletion of the FPS1 gene. The arsenite sensitive histone mutants also showed a lack of H3K4 methylation and reduced H4K16 acetylation. Altogether, we have identified the key residues in histone H3 and H4 proteins important for the regulation of Hog1 signaling, Fps1 activity, and ACR3 expression during arsenite stress.