MUS81 shares a high-degree homology with the catalytic XPF subunit of the XPF–ERCC1 endonuclease complex. It is catalytically active only when complexed with the regulatory subunits Mms4 or Eme1 in budding and fission yeasts, respectively, and EME1 or EME2 in humans. Although Mus81 complexes are implicated in the resolution of recombination intermediates in vivo, recombinant yeast Mus81-Mms4 and human MUS81-EME1 isolated from Escherichia coli fail to cleave intact Holliday junctions (HJs) in vitro. In this study, we show that human recombinant MUS81-EME2 isolated from E. coli cleaves HJs relatively efficiently, compared to MUS81-EME1. Furthermore, MUS81-EME2 catalyzed cleavage of nicked and gapped duplex deoxyribonucleic acids (DNAs), generating double-strand breaks. The presence of a 5′ phosphate terminus at nicks and gaps rendered DNA significantly less susceptible to the cleavage by MUS81-EME2 than its absence, raising the possibility that this activity could play a role in channeling damaged DNA duplexes that are not readily repaired into the recombinational repair pathways. Significant differences in substrate specificity observed with unmodified forms of MUS81-EME1 and MUS81-EME2 suggest that they play related but non-overlapping roles in DNA transactions.

Background:The biochemical function of variable N-terminal regions of eukaryotic Dna2 remains unclear. Results: The N-terminal 45-kDa domain of yeast Dna2 targets the enzyme specifically to a secondary structure flap. Conclusion:The hairpin binding activity of Dna2 contributes to efficient removal of hairpin flaps together with endonuclease and helicase activities during Okazaki fragment processing. Significance: The hairpin binding activity of Dna2 is critical for genome stability.

Background: How faulty Okazaki fragments are repaired remains unclear. Results: The DNA annealing activity of Rad52 and sister chromatid cohesion are important in the repair of faulty Okazaki fragments. Conclusion: Rad52/Rad59-mediated sister chromatid recombination is a major means of repairing faulty Okazaki fragments. Significance: The faithful repair of faulty Okazaki fragments is critical for genome stability.

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Defects in the mitochondrial genome (mitochondrial DNA (mtDNA)) are associated with both congenital and acquired disorders in humans. Nuclear-encoded DNA polymerase subunit gamma (POLG) plays an important role in mtDNA replication, and proofreading and mutations in POLG have been linked with increased mtDNA deletions. SSBP1 is also a crucial gene for mtDNA replication. Here, we describe a patient diagnosed with Pearson syndrome with large mtDNA deletions that were not detected in the somatic cells of the mother. Exome sequencing was used to evaluate the nuclear factors associated with the patient and his family, which revealed a paternal POLG mutation (c.868C > T) and a maternal SSBP1 mutation (c.320G > A). The patient showed lower POLG and SSBP1 expression than his healthy brothers and the general population of a similar age. Notably, c.868C in the wild-type allele was highly methylated in the patient compared to the same site in both his healthy brothers. These results suggest that the co- deficient expression of POLG and SSBP1 genes could contribute to the development of mtDNA deletion.

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Lagging strand synthesis is mechanistically far more complicated than leading strand synthesis because it involves multistep processes and requires considerably more enzymes and protein factors. Due to this complexity, multiple fail-safe factors are required to ensure successful replication of the lagging strand DNA. We attempted to identify novel factors that are required in the absence of the helicase activity of Dna2, an essential enzyme in Okazaki-fragment maturation. In this article, we identified Rim11, a GSK-3β-kinase homolog, as a multicopy suppressor of helicase-dead mutant (). Subsequent epistasis analysis revealed that Ume6 (a DNA binding protein, a downstream substrate of Rim11) also acted as a multicopy suppressor of the allele. We found that the interaction of Ume6 with the conserved histone deacetylase complex Sin3-Rpd3 and the catalytic activity of Rpd3 were indispensable for the observed suppression of the mutant. Moreover, multicopy suppression by Rim11/Ume6 requires the presence of sister-chromatid recombination mediated by Rad52/Rad59 proteins, but not vice versa. Interestingly, the overexpression of Rim11 or Ume6 also suppressed the MMS sensitivity of Δ. We also showed that the lethality of helicase-dead mutant was attributed to checkpoint activation and that decreased levels of deoxynucleotide triphosphates (dNTPs) by overexpressing Sml1 (an inhibitor of ribonucleotide reductase) rescued the mutant. We also present evidence that indicates Rim11/Ume6 works independently but in parallel with that of checkpoint inhibition, dNTP regulation, and sister-chromatid recombination. In conclusion, our results establish Rim11, Ume6, the histone deacetylase complex Sin3-Rpd3 and Sml1 as new factors important in the events of faulty lagging strand synthesis.

Background Hospital‐acquired pressure injuries are strongly associated with surgeries performed under general anesthesia. Aims The aim of this study was to evaluate the effects of using a prophylactic multi‐layer soft silicone foam dressing in non‐critically ill patients with a Braden Scale score of ≤18 after undergoing routine surgery without sacral pressure injuries. Methods This randomized controlled trial included 156 patients who were admitted for surgery under general anesthesia in a tertiary general hospital. The patients were divided into a control group and an intervention group. A 5‐layer soft silicone foam dressing was applied to the sacrum of patients in the intervention group immediately after surgery. For the control group, standard pressure injury prevention activities were performed alongside standard care without preventive dressings. Results There were no significant differences in general and clinical characteristics between the two groups; however, the incidence of pressure injury and blanching erythema was higher in the control group, showing a significant difference from the experimental group. Factors influencing the development of pressure injuries and blanching erythema through multivariate regression analysis were prophylactic dressing application and Braden Scale score at the time of admission. A statistically significant difference was noted in survival time from pressure injury between both groups. Linking Evidence to Action The incidence of pressure injuries and blanching erythema was lower when the prophylactic dressing was applied with standard protocol for general ward patients after surgery. Accurate evaluation of the patient's skin condition and pressure injury risk assessment before surgery are important. Progressive prophylactic dressings to prevent pressure injuries are effective, and tailored nursing interventions based on accurate assessment of patient's skin condition and risk factors are essential for maintaining skin integrity.