H2B oncohistones cause homologous recombination defect and genomic instability through reducing H2B monoubiquitination in Schizosaccharomyces pombe.

Canonical oncohistones are histone H3 mutations in the N-terminal tail associated with tumors and affect gene expression by altering H3 post-translational modifications (PTMs) and the epigenetic landscape. Noncanonical oncohistone mutations occur in both tails and globular domains of all 4 core histones and alter gene expression by perturbing chromatin remodeling. However, the effects and mechanisms of noncanonical oncohistones remain largely unknown. Here we characterized 16 noncanonical H2B oncohistones in the fission yeast Schizosaccharomyces pombe. We found that 7 of them exhibited temperature sensitivities and 11 exhibited genotoxic sensitivities. A detailed study of 2 of these onco-mutants H2BG52D and H2BP102L revealed that they were defective in homologous recombination (HR) repair with compromised histone eviction and Rad51 recruitment. Interestingly, their genotoxic sensitivities and HR defects were rescued by inactivation of the H2BK119 deubiquitination function of Ubp8 in the Spt-Ada-Gcn5-Acetyltransferase (SAGA) complex. The levels of H2BK119 monoubiquitination (H2Bub) in the H2BG52D and H2BP102L mutants are reduced in global and local DNA break sites presumably due to enhanced recruitment of Ubp8 onto nucleosomes, and are recovered upon loss of H2B deubiquitination function of the SAGA complex. Moreover, H2BG52D and H2BP102L heterozygotes exhibit genotoxic sensitivities and reduced H2Bub in cis. We therefore conclude that H2BG52D and H2BP102L oncohistones affect HR repair and genome stability via reduction of H2Bub and propose that other noncanonical oncohistones may also affect histone PTMs to cause diseases.

Structural and biochemical characterization of active sites mutant in human inorganic pyrophosphatase.

Inorganic pyrophosphatases (PPases) are enzymes that catalyze the conversion of inorganic pyrophosphate (PPi) into phosphate (Pi). Human inorganic pyrophosphatase 1 (Hu-PPase) exhibits high expression levels in a variety of tumors and plays roles in cell proliferation, apoptosis, invasion and metastasis, making it a promising prognostic biomarker and a target for cancer therapy. Despite its widespread presence, the catalytic mechanism of Hu-PPase in humans remains inadequately understood. The signature motif amino acid sequence (DXDPXD) within the active sites of PPases is preserved across different species. In this research, an enzymatic activity assay revealed that mutations led to a notable reduction in enzymatic function, although the impact of the four amino acids on the activity of the pocket varied. To investigate the influence of these residues on the substrate binding and enzymatic function of PPase, the crystal structure of the Hu-PPase-ED quadruple mutant (D116A/D118A/P119A/D121A) was determined at 1.69 Å resolution. The resulting structure maintained a barrel-like shape similar to that of the wild-type, albeit lacking Mg2+ ions. Molecular docking analysis demonstrated a decreased ability of Hu-PPase-ED to bind to PPi. Further, molecular dynamics simulation analysis indicated that the mutation rendered the loop of Mg2+ ion-binding residues less stable. Therefore, the effect on enzyme activity did not result from a change in the gross protein structure but rather from a mutation that abolished the Mg2+-coordinating groups, thereby eliminating Mg2+ binding and leading to the loss of enzyme activity.

Hypoglycemia associated with direct-acting anti-hepatitis C virus drugs: An epidemiologic surveillance study of the FDA adverse event reporting system (FAERS).

BACKGROUND AND OBJECTIVE: Hypoglycemia induced by direct-acting antiviral agents (DAAs) for chronic hepatitis C virus (HCV) infection is a rare but potentially life-threatening adverse reaction, which led to warnings by competent authorities. We therefore aimed to examine the hypoglycemic safety signal for DAAs. METHODS: Reports to the US Food and Drug Administration Adverse Event Reporting System (FAERS) from 1 October 2012 to 31 March 2020 were analyzed. The Medical Dictionary for Regulatory Activities was used to identify hypoglycemia cases. A case by non-case disproportionality approach was used whereby reporting odds ratio (ROR) with 95% confidence intervals (CI) were calculated. RESULTS: In HCV infection with diabetes patients, the cumulative frequency of hypoglycemic ADRs was 21.85/1000 for reports involving DAAs versus 13.50/1000 for reports involving other medications; For DAAs as a class drug, a nearly double increased reporting odds for hypoglycemia was observed (ROR: 1.63, 95% CI: 1.11-2.41). However, in DAAs subgroup analysis, only telaprevir (ROR: 1.66, 95% CI: 1.01-2.74) and elbasvir/grazoprevir (ROR: 2.25, 95% CI: 1.05-4.83) were associated with increased reporting risk of hypoglycemia during corresponding marketing period; when combined with insulins and sulfonylureas, DAAs were associated with increased reporting risk for hypoglycemia (ROR: 1.98, 95% CI: 1.36-2.88; ROR: 1.62, 95% CI: 1.06-2.48), but concomitant biguanides, dipeptidyl peptidase IV (DPP-4) inhibitors or glucagon-like peptide-1 receptor agonists (GLP-1RAs) were not significant. CONCLUSIONS: This study supports the current recommendation for cautious about hypoglycemic risk relating to the use of DAAs. Treatment with DAAs and antidabetic agents (especially insulins and sulfonylureas) will increase hypoglycemia reporting risk. Physicians and pharmacists should be aware of this risk when prescribing DAAs for patients suffering from diabetes, advanced age or liver decompensation.

Effectively Improve the Astaxanthin Production by Combined Additives Regulating Different Metabolic Nodes in Phaffia rhodozyma.

Astaxanthin is an important natural resource that is widely found in marine environments. Metabolic regulation is an effective method for improving astaxanthin production in Phaffia rhodozyma. Most studies have focused on single regulators, which have limited effects. In this study, 16 metabolic regulators were screened to improve astaxanthin production in high-yield and wild-type strains. Fluconazol and glutamic acid increased astaxanthin volumetric yield in MVP14 by 25.8 and 30.9%, respectively, while ethanol increased astaxanthin volumetric yield in DSM626, 29.3%. Furthermore, six additives that inhibit the competing pathways and promote the main pathway for astaxanthin synthesis were selected for combination treatment. We found that the optimal combination was penicillin, ethanol, triclosan, and fluconazol, which increased astaxanthin cell yield by 51%. Therefore, we suggest that simultaneously promoting the master pathways (mevalonate) and inhibiting competing pathways (fatty acid synthesis and ergosterol) is the best strategy to improve astaxanthin cell yield. Moreover, regulators of the biomass pathway should be avoided to improve cell yield. This study provides a technical basis for the utilisation of astaxanthin in P. rhodozyma.