Replication Process Research Articles

Concurrent D-loop cleavage by Mus81 and Yen1 yields half-crossover precursors.

Homologous recombination involves the formation of branched DNA molecules that may interfere with chromosome segregation. To resolve these persistent joint molecules, cells rely on the activation of structure-selective endonucleases (SSEs) during the late stages of the cell cycle. However, the premature activation of SSEs compromises genome integrity, due to untimely processing of replication and/or recombination intermediates. Here, we used a biochemical approach to show that the budding yeast SSEs Mus81 and Yen1 possess the ability to cleave the central recombination intermediate known as the displacement loop or D-loop. Moreover, we demonstrate that, consistently with previous genetic data, the simultaneous action of Mus81 and Yen1, followed by ligation, is sufficient to recreate the formation of a half-crossover precursor in vitro. Our results provide not only mechanistic explanation for the formation of a half-crossover, but also highlight the critical importance for precise regulation of these SSEs to prevent chromosomal rearrangements.

Principles of amyloplast replication in the ovule integuments of Arabidopsis thaliana.

Plastids in vascular plants have various differentiated forms, among which amyloplasts are crucial for starch storage and plant productivity. Despite the vast knowledge of the binary-fission mode of chloroplast division, our understanding of the replication of non-photosynthetic plastids, including amyloplasts, remains limited. Recent studies have suggested the involvement of stromules (stroma-filled tubules) in plastid replication when the division apparatus is faulty. However, details of the underlying mechanism(s) and their relevance to normal processes have yet to be elucidated. Here, we developed a live analysis system for studying amyloplast replication using Arabidopsis (Arabidopsis thaliana) ovule integuments. We showed the full sequence of amyloplast development and demonstrated that wild-type amyloplasts adopt three modes of replication, binary fission, multiple fission, and stromule-mediated fission, via multi-way placement of the FtsZ ring. The minE mutant, with severely inhibited chloroplast division, showed marked heterogeneity in amyloplast size, caused by size-dependent but wild-type modes of plastid fission. The dynamic properties of stromules distinguish the wild-type and minE phenotypes. In minE cells, extended stromules from giant amyloplasts acquired stability, allowing FtsZ ring assembly and constriction, as well as the growth of starch grains therein. Despite hyper-stromule formation, amyloplasts did not proliferate in the ftsZ null mutant. These data clarify the differences between amyloplast and chloroplast replication and demonstrate that the structural plasticity of amyloplasts underlies the multiplicity of their replication processes. Furthermore, this study shows that stromules can generate daughter plastids via the assembly of the FtsZ ring.

Transforming evidence-based clinical guidelines into implementable clinical decision support services: the CAREPATH study for multimorbidity management.

The CAREPATH Project aims to develop a patient-centered integrated care platform tailored to older adults with multimorbidity, including mild cognitive impairment (MCI) or mild dementia. Our goal is to empower multidisciplinary care teams to craft personalized holistic care plans while adhering to evidence-based guidelines. This necessitates the creation of clear specifications for clinical decision support (CDS) services, consolidating guidance from multiple evidence-based clinical guidelines. Thus, a co-creation approach involving both clinical and technical experts is essential. This paper outlines a robust methodology for generating implementable specifications for CDS services to automate clinical guidelines. We have established a co-creation framework to facilitate collaborative exploration of clinical guidelines between clinical experts and software engineers. We have proposed an open, repeatable, and traceable method for translating evidence-based guideline narratives into implementable specifications of CDS services. Our approach, based on international standards such as CDS-Hooks and HL7 FHIR, enhances interoperability and potential adoption of CDS services across diverse healthcare systems. This methodology has been followed to create implementable specifications for 65 CDS services, automating CAREPATH consensus guideline consolidating guidance from 25 selected evidence-based guidelines. A total of 296 CDS rules have been formally defined, with input parameters defined as clinical concepts bound to FHIR resources and international code systems. Outputs include 346 well-defined CDS Cards, offering clear guidance for care plan activities and goal suggestions. These specifications have led to the implementation of 65 CDS services integrated into the CAREPATH Adaptive Integrated Care Platform. Our methodology offers a systematic, replicable process for generating CDS specifications, ensuring consistency and reliability across implementation. By fostering collaboration between clinical expertise and technical proficiency, we enhance the quality and relevance of generated specifications. Clear traceability enables stakeholders to track the development process and ensure adherence to guideline recommendations.

Physical education research trend in the last 100 years: bibliometric analysis and systematic review of Scopus journal database

This study carried out a bibliometric analysis and systematic review of the trends in physical education research during the previous 100 years using the Scopus journal database. This research aims to map the academic progress of the discipline and highlight the conceptual and methodological alterations that have occurred. Using the Scopus journal database, papers related to physical education published in the last 100 years were compiled for this bibliometric analysis. Using "physical education" as a search phrase, the article search limited the results to publications published between 1924 and 2023. Exclusion criteria were used to weed out publications that had no relevance to the research's primary topic. Based on their importance and pertinence, 217 articles from a preliminary screening of 43,238 were selected for additional review. Next, this data was examined using the VOS viewer program to look for trends, citation patterns, and institutional contributions. The literature review method was also applied to the top 10 papers, with one being selected as the most cited article over a ten-year period. The literature review approach followed PRISMA guidelines to ensure an open and replicable article selection process. The study's findings demonstrate how physical education has evolved significantly from its original emphasis on militaristic and physical components to a more inclusive and technologically advanced approach that incorporates mental health and inclusion. The study's conclusions provide a standard for further investigation into this field by confirming the value of physical education in promoting both academic achievement and general well-being. Keywords: holistic approach, educational inclusivity, technological development, educational diversity, physical activity, physical fitness.

Transparency, reproducibility, and replicability of pharmacoepidemiology studies in a distributed network environment.

Our objective is to describe how the U.S. Food and Drug Administration (FDA)'s Sentinel System implements best practices to ensure trust in drug safety studies using real-world data from disparate sources. We present a stepwise schematic for Sentinel's data harmonization, data quality check, query design and implementation, and reporting practices, and describe approaches to enhancing the transparency, reproducibility, and replicability of studies at each step. Each Sentinel data partner converts its source data into the Sentinel Common Data Model. The transformed data undergoes rigorous quality checks before it can be used for Sentinel queries. The Sentinel Common Data Model framework, data transformation codes for several data sources, and data quality assurance packages are publicly available. Designed to run against the Sentinel Common Data Model, Sentinel's querying system comprises a suite of pre-tested, parametrizable computer programs that allow users to perform sophisticated descriptive and inferential analysis without having to exchange individual-level data across sites. Detailed documentation of capabilities of the programs as well as the codes and information required to execute them are publicly available on the Sentinel website. Sentinel also provides public trainings and online resources to facilitate use of its data model and querying system. Its study specifications conform to established reporting frameworks aimed at facilitating reproducibility and replicability of real-world data studies. Reports from Sentinel queries and associated design and analytic specifications are available for download on the Sentinel website. Sentinel is an example of how real-world data can be used to generate regulatory-grade evidence at scale using a transparent, reproducible, and replicable process.

Integrated re-analysis of transcriptomic and proteomic datasets reveals potential mechanisms for Zika viral-based oncolytic therapy in neuroblastoma.

Paediatric neuroblastoma and brain tumours account for a third of all childhood cancer-related mortality. High-risk neuroblastoma is highly aggressive and survival is poor despite intensive multi-modal therapies with significant toxicity. Novel therapies are desperately needed. The Zika virus (ZIKV) can access the nervous system and there is growing interest in employing ZIKV as a potential therapy against paediatric nervous system tumours, including neuroblastoma. Here, we perform extensive data mining, integration and re-analysis of ZIKV infection datasets to highlight molecular mechanisms that may govern the oncolytic response in neuroblastoma cells. We collate infection data of multiple neuroblastoma cell lines by different ZIKV strains from a body of published literature to inform the susceptibility of neuroblastoma to the ZIKV oncolytic response. Integrating published transcriptomics, interaction proteomics, dependency factor and compound datasets we propose the involvement of multiple host systems during ZIKV infection. Through data mining of published literature, we observed most paediatric neuroblastoma cell lines to be highly susceptible to ZIKV infection and propose the PRVABC59 ZIKV strain to be the most promising candidate for neuroblastoma oncolytic virotherapy. ZIKV induces TNF signalling, lipid metabolism, the Unfolded Protein Response (UPR), and downregulates cell cycle and DNA replication processes. ZIKV infection is dependent on sterol regulatory element binding protein (SREBP)-regulated lipid metabolism and three protein complexes; V-ATPase, ER Membrane Protein Complex (EMC) and mammalian translocon. We propose ZIKV non-structural protein 4B (NS4B) as a likely mediator of ZIKVs interaction with IRE1-mediated UPR, lipid metabolism and mammalian translocon. Our work provides a significant understanding of ZIKV infection in neuroblastoma cells, which will facilitate the progression of ZIKV-based oncolytic virotherapy through pre-clinical research and clinical trials.

Optimization of the lost PLA production process for the manufacturing of Al-alloy porous structures: Recent developments, macrostructural and microstructural analysis

The main task of this work is the optimization of the manufacturing process of Al-alloy lattice cellular structures with rhombic cell, obtained with lost-PLA technique. It is an easy, environment sustainable and economical technique (both for infrastructure and operating costs) for the manufacturing of Al porous structure based on the 3D printing of PLA and replication process alternative to that based on expensive metal 3D printers. Plaster processing, PLA burnout and AA 6082 alloy casting conditions and parameters have been suitably tuned in order to get final samples with geometry and surface finishing conditions identical to the starting ones made in PLA. A good replication process has been implemented with a high repeatability rate and accurate surface finishing, comparable with that of the PLA printed objects. Morphological analysis on PLA and Al 6082 was conducted as well microstructural analysis and Vickers microhardness tests on Al alloy samples in the as-cast conditions. Metallography reveals the presence of AlFeSi and AlFeMnSi intermetallic phases at the cell boundaries and some coarse precipitates Mg2Si in the AA 6082 alloy. Microstructures and HV measured values are aligned with literature data for this alloy in the same (as-cast) conditions.

Exploring the Motivation, Process, and Barriers for Replication of a Special Education Advocacy Program

AbstractSpecial education advocacy programs educate and empower individuals to become advocates for families of school-aged children with disabilities. Although special education advocacy programs are becoming more common across the globe, replication and wide scale implementation are needed to determine their credibility. The purpose of this study was to explore the replication of a special education advocacy program, the Volunteer Advoacy Project (VAP), to understand the motivation, process, and barriers to replication for community-based agencies. Participants included the staff of ten community-based agencies that submitted a proposal to replicate the VAP but did not receive funding to support the replication process. Applications, transcripts, emails, and field-notes were used to conduct qualitative data analysis and determine themes. Findings showed common motivations and a cyclical replication process. Common barriers related to limited: capacity and funding. Implications for research, policy, and practice are discussed.

Clinical Significance of a Novel Vasculogenic Mimicry-Based Prognostic Model in Hepatocellular Carcinoma.

Vasculogenic mimicry, a novel neovascularization pattern of aggressive tumors, is associated with poor clinical outcomes. The aim of this research was to establish a new model, termed VC score, to predict the prognosis, Tumor Microenvironment (TME) components, and immunotherapeutic response in Hepatocellular Carcinoma (HCC). The expression data of the public databases were used to develop the prognostic model. Consensus clustering was performed to confirm the molecular subtypes with ideal clustering efficacy. The high- and low-risk groups were stratified utilizing the VC score. Various methodologies, including survival analysis, single-sample Gene Set Enrichment Analysis (ssGSEA), Tumor Immune Dysfunction and Exclusion scores (TIDE), Immunophenoscore (IPS), and nomogram, were utilized for verification of the model performance and to characterize the immune status of HCC tissues. GSEA was performed to mine functional pathway information. The survival and immune characteristics varied between the three molecular subtypes. A five-gene signature (TPX2, CDC20, CFHR4, SPP1, and NQO1) was verified to function as an independent predictive factor for the prognosis of patients with HCC. The high-risk group exhibited lower Overall Survival (OS) rates and higher mortality rates in comparison to the low-risk group. Patients in the low-risk group were predicted to benefit from immune checkpoint inhibitor therapy and exhibit increased sensitivity to immunotherapy. Enrichment analysis revealed that signaling pathways linked to the cell cycle and DNA replication processes exhibited enrichment in the high-risk group. The VC score holds the potential to establish individualized treatment plans and clinical management strategies for patients with HCC.

Repurposing of antimycobacterium drugs for COVID-19 treatment by targeting SARS CoV-2 main protease: An in-silico perspective

The global mortality rate has been significantly impacted by the COVID-19 pandemic, caused by the SARS CoV-2 virus. Although the pursuit for a potent antiviral is still in progress, experimental therapies based on repurposing of existing drugs is being attempted. One important therapeutic target for COVID-19 is the main protease (Mpro) that cleaves the viral polyprotein in its replication process. Recently minocycline, an antimycobacterium drug, has been successfully implemented for the treatment of COVID-19 patients. But it’s mode of action is still far from clear. Furthermore, it remains unresolved whether alternative antimycobacterium drugs can effectively regulate SARS CoV-2 by inhibiting the enzymatic activity of Mpro. To comprehend these facets, eight well-established antimycobacterium drugs were put through molecular docking experiments. Four of the antimycobacterium drugs (minocycline, rifampicin, clofazimine and ofloxacin) were selected by comparing their binding affinities towards Mpro. All of the four drugs interacted with both the catalytic residues of Mpro (His41 and Cys145). Additionally, molecular dynamics experiments demonstrated that the Mpro-minocyline complex has enhanced stability, experiences reduced conformational fluctuations and greater compactness than other three Mpro-antimycobacterium and Mpro-N3/lopinavir complexes. This research furnishes evidences for implementation of minocycline against SARS CoV-2. In addition, our findings also indicate other three antimycobacterium/antituberculosis drugs (rifampicin, clofazimine and ofloxacin) could potentially be evaluated for COVID-19 therapy.

Fostering Digital Communities

As online education expands, fostering digital communities that support networked learning becomes imperative. However, many universities lack comprehensive digital strategies to facilitate engagement and connections in distributed environments. This research examines the development of an inaugural digital master plan at a university where half of the student population is online. Guided by Moore's theory of interactions (1989) and Garrison's Community of Inquiry framework (2017), the plan aimed to enable meaningful student-to-content, student-to-instructor, and student-to-student interactions. The digital master plan was designed to provide high-level guidance on the intentional and purposeful use of the educational technologies, tools, platforms, and systems necessary for a robust online learning experience. It creates a cohesive vision and strategy for the digital learning experience, just as a campus master plan aligns the physical learning spaces. The digital master plan leverages the Community of Inquiry framework as a key reference point in its comprehensive gap analysis. The collaborative process involved multiple methods to assess gaps in the university’s infrastructure including: National Survey of Student Engagement (NSSE) data, three internal surveys, an external diagnostic analysis and plan, and audits of the learning management system's tools and usage. Quantitative data provided insights into student perceptions, while qualitative findings explored the depth of social relationships and learning networks enabled through digital platforms. Throughout the process, the research team aimed to understand the social learning processes that support how learners develop and utilize technology to learn and foster a sense of belonging (Garrison, 2017). The process harnesses the natural motivations underpinning social network formation - namely information sharing, support seeking, and sense of belonging. Further, it operationalizes these motivations to achieve CoI's high-order learning community goals. Analysis revealed key gaps related to: clearly defining and measuring online student success, expanding engagement opportunities in courses, leveraging technologies to facilitate connections, building a collaborative faculty culture, and improving communication. In response, the final digital master plan put forth five recommendations focused on these priority areas. Implementation and evaluation of digital platforms aligned to the recommendations indicate positive impacts on online students' sense of connectedness, learning experience, and academic performance. This research makes important theoretical and practical contributions by developing a replicable institutional process for assessing and strategically enhancing a digital ecosystem to foster networked learning. The digital master plan provides guidance for the adoption of social technologies and pedagogies to increase community, connectivity, and collaboration. As online education continues to expand, insights from this case study can inform strategic digital planning efforts at other universities striving to overcome transactional distance and cultivate impactful virtual learning communities.

Computational design, docking, and molecular dynamics simulation study of RNA helicase inhibitors of dengue virus.

RNA viruses are complex pathogens in terms of their genetic makeup, mutation frequency, and transmission modes. They contain the RNA helicase enzyme, which plays a crucial role in the viral genome replication process. This work aims to develop and screen a potential molecule that could function as a dengue virus (DENV) RNA helicase inhibitor. The present study was performed by taking 26 potential derivatives of gedunin phytochemicals from the PubChem database as ligands. The binding study of the compounds were analyzed by in silico docking method considering DENV RNA helicase enzyme as the receptor. After a thorough analysis of the docking scores, toxicity, and physicochemical properties, compound tetrahydrogedunin was obtained as the best. Based on tetrahydrogedunin molecular structure, 100 drug-like molecules were designed using the Data Warrior tool. After the screening process for drug-likeness and ADMET properties, the derivative number 42 was considered as the promising. Further comparative docking of derivative 42 and a standard inhibitor molecule ST-610 with DENV RNA helicase enzyme showed binding affinity as -10.0 kcal/mol and -9.6 kcal/mol, respectively. The favorable interaction between DENV RNA helicase and derivative 42 was further validated by 50 nanoseconds molecular dynamics simulation and MM-GBSA analysis. Since the antiviral activity of derivative 42 has not been reported till date, the compound was predicted as a novel therapeutic molecule that can act against the dengue virus (DENV) RNA helicase enzyme.

Anticancer Activity of Novel 1,3,4-oxadiazole Derivatives against PARP-1 Inhibitors: An In-silico Approach

Background: Nuclear enzyme poly (ADP-ribose) polymerase-1 (PARP-1) controls the cell cycle, DNA repair, transcription, and replication processes. In this study, olaparib and rucaparib have been taken as standard drugs for comparison of results. As per previous research data, 1,3,4-Oxadiazole moiety has multidirectional biological activity and shows high activity against cancer. Objective: This study aimed to carry out the in silico ligand-based screening for the identification of hits for PARP1 inhibitors bearing 1,3,4-thiadiazole derivatives using Schrodinger suite 2022-1 and to perform MMGBSA and molecular dynamics simulation for lead molecules. Methods: A total of 32 derivatives of 1,3,4-Oxadiazole were designed with four different acids: phenoxy acetic acid, 1-Naphthoxy acetic acid, 2-Naphthoxy acetic acid, and piperonylic acid. Molecular docking (XP) studies were performed between 4ZZZ.pdb and the designed analogues, and the binding affinity values lay in the range of -8.52 to -3.52 kcal/mol. 2D interactions between the protein and the ligand were observed. Based on the binding affinity values and ADMET results, top 10 analogues were selected for performing MM-GBSA. Results: The dG-bind score of the top compounds varied from -2.30 to -60.67 kcal/mol, and analogue D4 was selected for MD simulation studies for 100ns. Results of Molecular dynamics (MD) studies showed that D4 interacted with amino acid residues, and the ligand-protein interaction stabilized from 58-90ns. The in silico study's findings suggested that the chemicals A1, A3, B1, B2, B3, B4, C1, C6, D1, and D4 might be significantly active against breast cancer with potential therapeutic benefits and are likely to be useful after further development. Conclusion: In conclusion, numerous molecules exhibit a high affinity for PARP-1 when derived from 1,3,4-oxadiazole. The in silico study's findings suggested that the chemicals A1, A3, B1, B2, B3, B4, C1, C6, D1, and D4 might be significantly active against breast cancer with potential therapeutic benefits and are likely to be useful after further development.

The Terminase Complex of Each Human Herpesvirus.

The human herpesviruses (HHVs) are classified into the following three subfamilies: Alphaherpesvirinae, Betaherpesvirinae, and Gammaherpesvirinae. These HHVs have distinct pathological features, while containing a highly conserved viral replication pathway. Among HHVs, the basic viral particle structure and the sequential processes of viral replication are nearly identical. In particular, the capsid formation mechanism has been proposed to be highly similar among herpesviruses, because the viral capsid-organizing proteins are highly conserved at the structural and functional levels. Herpesviruses form capsids containing the viral genome in the nucleus of infected cells during the lytic phase, and release infectious virus (i.e., virions) to the cell exterior. In the capsid formation process, a single-unit-length viral genome is encapsidated into a preformed capsid. The single-unit-length viral genome is produced by cleavage from a viral genome precursor in which multiple unit-length viral genomes are tandemly linked. This encapsidation and cleavage is carried out by the terminase complex, which is composed of viral proteins. Since the terminase complex-mediated encapsidation and cleavage is a virus-specific mechanism that does not exist in humans, it may be an excellent inhibitory target for anti-viral drugs with high virus specificity. This review provides an overview of the functions of the terminase complexes of HHVs.

The fungicide pyraclostrobin affects gene expression by altering the DNA methylation pattern in Magnaporthe oryzae.

Rice blast disease caused by Magnaporthe oryzae has long been the main cause of rice (Oryza sativa L.) yield reduction worldwide. The quinone external inhibitor pyraclostrobin is widely used as a fungicide to effectively control the spread of pathogenic fungi, including M. oryzae. However, M. oryzae can develop resistance through multiple levels of mutation, such as target protein cytb mutation G143A/S, leading to a decrease in the effectiveness of the biocide after a period of application. Therefore, uncovering the possible mutational mechanisms from multiple perspectives will further provide feasible targets for drug development. In this work, we determined the gene expression changes in M. oryzae in response to pyraclostrobin stress and their relationship with DNA methylation by transcriptome and methylome. The results showed that under pyraclostrobin treatment, endoplasmic reticulum (ER)-associated and ubiquitin-mediated proteolysis were enhanced, suggesting that more aberrant proteins may be generated that need to be cleared. DNA replication and repair processes were inhibited. Glutathione metabolism was enhanced, while lipid metabolism was impaired. The number of alternative splicing events increased. These changes may be related to the elevated methylation levels of cytosine and adenine in gene bodies. Both hypermethylation and hypomethylation of differentially methylated genes (DMGs) mainly occurred in exons and promoters. Some DMGs and differentially expressed genes (DEGs) were annotated to the same pathways by GO and KEGG, including protein processing in the ER, ubiquitin-mediated proteolysis, RNA transport and glutathione metabolism, suggesting that pyraclostrobin may affect gene expression by altering the methylation patterns of cytosine and adenine. Our results revealed that 5mC and 6mA in the gene body are associated with gene expression and contribute to adversity adaptation in M. oryzae. This enriched the understanding for potential mechanism of quinone inhibitor resistance, which will facilitate the development of feasible strategies for maintaining the high efficacy of this kind of fungicide.

Influence of the Type of Mathematical Problems on Students’ and Pre-service Teachers’ Interest and Performance. A Replication and Elaboration Study

Influence of the Type of Mathematical Problems on Students’ and Pre-service Teachers’ Interest and Performance. A Replication and Elaboration Study

Triggering Degradation of Host Cellular Proteins for Robust Propagation of Influenza Viruses.

Following infection, influenza viruses strive to establish a new host cellular environment optimized for efficient viral replication and propagation. Influenza viruses use or hijack numerous host factors and machinery not only to fulfill their own replication process but also to constantly evade the host's antiviral and immune response. For this purpose, influenza viruses appear to have formulated diverse strategies to manipulate the host proteins or signaling pathways. One of the most effective tactics is to specifically induce the degradation of the cellular proteins that are detrimental to the virus life cycle. Here, we summarize the cellular factors that are deemed to have been purposefully degraded by influenza virus infection. The focus is laid on the mechanisms for the protein ubiquitination and degradation in association with facilitated viral amplification. The fate of influenza viral infection of hosts is heavily reliant on the outcomes of the interplay between the virus and the host antiviral immunity. Understanding the processes of how influenza viruses instigate the protein destruction pathways could provide a foundation for the development of advanced therapeutics to target host proteins and conquer influenza.

MutL Activates UvrD by Interaction Between the MutL C-terminal Domain and the UvrD 2B Domain

UvrD is a helicase vital for DNA replication and quality control processes. In its monomeric state, UvrD exhibits limited helicase activity, necessitating either dimerization or assistance from an accessory protein to efficiently unwind DNA. Within the DNA mismatch repair pathway, MutL plays a pivotal role in relaying the repair signal, enabling UvrD to unwind DNA from the strand incision site up to and beyond the mismatch. Although this interdependence is well-established, the precise mechanism of activation and the specific MutL-UvrD interactions that trigger helicase activity remain elusive. To address these questions, we employed site-specific crosslinking techniques using single-cysteine variants of MutL and UvrD followed by functional assays. Our investigation unveils that the C-terminal domain of MutL not only engages with UvrD but also acts as a self-sufficient activator of UvrD helicase activity on DNA substrates with 3′-single-stranded tails. Especially when MutL is covalently attached to the 2B or 1B domain the tail length can be reduced to a minimal substrate of 5 nucleotides without affecting unwinding efficiency.

Adaptive use of error-prone DNA polymerases provides flexibility in genome replication during tumorigenesis.

Human cells possess many different polymerase enzymes, which collaborate in conducting DNA replication and genome maintenance to ensure faithful duplication of genetic material. Each polymerase performs a specialized role, together providing a balance of accuracy and flexibility to the replication process. Perturbed replication increases the requirement for flexibility to ensure duplication of the entire genome. Flexibility is provided via the use of error-prone polymerases, which maintain the progression of challenged DNA replication at the expense of mutagenesis, an enabling characteristic of cancer. This review describes our recent understanding of mechanisms that alter the usage of polymerases during tumorigenesis and examines the implications of this for cell survival and tumor progression. Although expression levels of polymerases are often misregulated in cancers, this does not necessarily alter polymerase usage since an additional regulatory step may govern the use of these enzymes. We therefore also examine how the regulatory mechanisms of DNA polymerases, such as Rad18-mediated PCNA ubiquitylation, may impact the functionalization of error-prone polymerases to tolerate oncogene-induced replication stress. Crucially, it is becoming increasingly evident that cancer cells utilize error-prone polymerases to sustain ongoing replication in response to oncogenic mutations which inactivate key DNA replication and repair pathways, such as BRCA deficiency. This accelerates mutagenesis and confers chemoresistance, but also presents a dependency that can potentially be exploited by therapeutics.

Research progress on the effect of hepatitis B virus DNA integration on antiviral therapy

Hepatitis B virus (HBV) DNA integration occurs during the reverse transcription process of HBV replication, which develops in the early stages of HBV infection and accompanies the entire disease course. The integration of HBV DNA is detrimental to the attainment of clinical cure goals and also raises the risk of developing liver cancer. Theoretically, nucleos(t)ide analogs can reduce the synthesis of new double-stranded linear DNA, but there is no clearance function for hepatocytes that have already integrated HBV. Therefore, patients with serum HBV DNA-negative conversions still have the risk of developing liver cancer. As an immunomodulatory drug, interferon can not only inhibit viral replication but also inhibit or even eliminate existing clonally amplified hepatocytes carrying integrated HBV DNA fragments. However, there are currently few studies on the effects of nucleos(t)ide analogues and interferon therapy on HBV DNA integration. Thus, large-scale clinical studies are urgently needed for further clarification.