Elevated dNTP levels suppress hyper-recombination in Saccharomyces cerevisiae S-phase checkpoint mutants

MEC1, the essential yeast homolog of the human ATR/ATM genes, controls the S-phase checkpoint and prevents replication fork collapse at slow zones of DNA replication. The viability of hypomorphic mec1-21 is reduced in the rad52 mutant, defective in homologous recombination, suggesting that replication generates recombinogenic lesions. We previously observed a 6-, 10- and 30-fold higher rate of spontaneous sister chromatid exchange (SCE), heteroallelic recombination and translocations, respectively, in mec1-21 mutants compared to wild-type. Here we report that the hyper-recombination phenotype correlates with lower deoxyribonucleoside triphosphate (dNTP) levels, compared to wild-type. By introducing a dun1 mutation, thus eliminating inducible expression of ribonucleotide reductase in mec1-21, rates of spontaneous SCE increased 15-fold above wild-type. All the hyper-recombination phenotypes were reduced by SML1 deletions, which increase dNTP levels. Measurements of dNTP pools indicated that, compared to wild-type, there was a significant decrease in dNTP levels in mec1-21, dun1 and mec1-21 dun1, while the dNTP levels of mec1-21 sml1, mec1-21 dun1 sml1 and sml1 mutants were ∼2-fold higher. Interestingly, higher dNTP levels in mec1-21 dun1 sml1 correlate with ∼2-fold higher rate of spontaneous mutagenesis, compared to mec1-21 dun1. We suggest that higher dNTP levels in specific checkpoint mutants suppress the formation of recombinogenic lesions

Transcriptional Response of Yeast to Aflatoxin B(1): Recombinational Repair Involving RAD51 and RAD1

The potent carcinogen aflatoxin B(1) is a weak mutagen but a strong recombinagen in Saccharomyces cerevisiae. Aflatoxin B(1) exposure greatly increases frequencies of both heteroallelic recombination and chromosomal translocations. We analyzed the gene expression pattern of diploid cells exposed to aflatoxin B(1) using high-density oligonucleotide arrays comprising specific probes for all 6218 open reading frames. Among 183 responsive genes, 46 are involved in either DNA repair or in control of cell growth and division. Inducible growth control genes include those in the TOR signaling pathway and SPO12, whereas PKC1 is downregulated. Eleven of the 15 inducible DNA repair genes, including RAD51, participate in recombination. Survival and translocation frequencies are reduced in the rad51 diploid after aflatoxin B(1) exposure. In mec1 checkpoint mutants, aflatoxin B(1) exposure does not induce RAD51 expression or increase translocation frequencies; however, when RAD51 is constitutively overexpressed in the mec1 mutant, aflatoxin B(1) exposure increased translocation frequencies. Thus the transcriptional profile after aflatoxin B(1) exposure may elucidate the genotoxic properties of aflatoxin B(1)

Surface Engineering Strategy Enables 4.5 V Sulfide-Based All-Solid-State Batteries with High Cathode Loading and Long Cycle Life

Sulfide-based all-solid-state lithium batteries (ASSLBs) with LiCoO2 (LCO) operating at high voltage (≥4.5 V vs Li+/Li) hold promise in realizing high energy density while maintaining safety. Here, we propose a solid electrolyte coating strategy to stabilize the cathode electrolyte interface and demonstrate the benefit of lithium difluoro(oxalate)borate (LiDFOB) as coating layer on the surface of Li6PS5Cl (LPSCl) to improve the performance of LCO at 4.5 V. 89.3% of initial discharge capacity can be retained after 1500 cycles at 1C (1C = 150 mA g–1). ASSLBs with high cathode loading (35.7 mg cm–2) could deliver an areal capacity over 6 mAh cm–2 (167 mAh g–1) at 0.1C and keep 85% capacity retention after 200 cycles at 0.3C. The investigation of the improvement mechanism further verifies that in situ decomposition of LiDFOB would build an (electro)chemomechanically stable interface, which not only suppresses interfacial side reactions but also buffers the cathode cracking

Ethnoracial Disparities in Rates of Non-Natural Causes of Death After the 2020 COVID-19 Outbreak in New York State

Introduction: COVID-19 was associated with increases in non-natural cause mortality in the U.S., including deaths due to drug overdose, homicide, and motor vehicle crashes. Initial reports indicated higher rates of non-natural mortality among ethnoracial minority groups. This report aims to clarify these disparities by documenting trends in non-natural mortality across ethnoracial groups during the 2020 COVID-19 surge in New York State. Methods: We report monthly trends in non-natural cause mortality (overall and stratified by ethnoracial status) in New York State from January 2019 through December 2020, which included the COVID-19 onset in March 2020. Results: Total mean monthly unintentional overdose rates per 100,000 increased from 17.45 (before surge: January 2019–February 2020) to 23.19 (after surge: March 2020–December 2020) (mean difference=5.73, 95% CI=3.82, 7.65; p<0.001). Mean monthly homicide death rates increased from 2.34 before surge to 3.55 after surge (mean difference=1.20, 95% CI=0.60, 1.81; p<0.001), with the increase seen primarily in the non-Latinx Black population. Although increasing unintentional overdose death rates before surge equally affected non-Latinx White, Latinx, and non-Latinx Black persons, they remained high for non-Latinx Black persons but dropped for the other 2 groups after the pandemic onset. None of the ethnoracial subgroups showed significant increases in suicide or motor vehicle crash death rates. Conclusions: Non-Latinx Black persons showed disproportionately high and sustained increased rates of unintentional overdose and homicide death rates after the 2020 COVID-19 surge in New York State. Fatality review and death scene investigation research is needed to better understand these disparities