1,720,971 research outputs found
Dengue Virus Modulation Of Genome Instability In Vero E6 Cells
Full text linkDengue virus (DENV) is the fastest-spreading arthropod-borne virus in the world. Dengue is characterized as a major global public health challenge in tropical and subtropical nations by the World Health Organization. The number of dengue cases globally has increased 8-fold in the past two decades, with 100 to 400 million cases occurring annually. While most patients with dengue fever are asymptomatic, dengue infection carries the possibility of severe and potentially fatal febrile illness. Approximately 1 in 4 individuals infected with dengue virus develop symptomatic dengue infection, often presenting as mild to moderate, nonspecific, acute febrile illness. A smaller subset of these individuals, about 1 in 20 infected with DENV, go on to develop severe dengue. Dengue fever is characterized by a high fever, headache, rash, myalgia, arthralgia, and stomachache. Dengue fever can progress into severe dengue, characterized by thrombocytopenia, vascular leakage, hypotension, and potentially fatal hypovolemic shock. Given the COVID-19 pandemic, RNA virus research has been spotlighted across several fields, including DNA repair and genome instability. Recently, we have shown that SARS-CoV-2, an enveloped, positive sense RNA virus of the Coronaviridae family, triggers a DNA damage response in host cells and upregulates genome instability markers in human lung cells, Golden Syrian Hamster lung tissues, COVID-19 autopsy lung tissues, and blood sera from patients with acute COVID-19 and post-COVID. Specifically, we observed host cell genetic alterations, such as increased HPRT-mutagenesis, telomere length dysregulation, and elevated microsatellite instability (MSI). In addition to this, emerging evidence has suggested that DENV-dependent modulation of host cell genome instability should be investigated. It is known that viruses of the Flaviviridae family, including DENV, trigger oxidative stress, which has been implicated in the pathogenesis of many diseases and cancers. Considering this, a recent preliminary study discovered a positive correlation between DNA damage, apoptosis, and oxidative stress during DENV infection. Epidemiologically, in 2020, a population-based cohort study through the National Health Insurance Research Databases in Taiwan provided the first epidemiologic evidence for the association between dengue virus infection and leukemia, suggesting a possible association between DENV infection and cancer incidence. Here, we report host genome instability post-DENV infection in Vero E6 cells, as observed by global repression of DNA repair pathways. Specifically, we report suppression of essential homologous recombination, mismatch repair, Fanconi anemia, non-homologous end joining, base excision repair, nucleotide excision repair, DNA damage response, and cellular stress response genes. In addition, we see an increase in the mutagenic translesion synthesis polymerase, POL1. Strikingly, we discovered pre-treatment with JH-RE-06.NaOH, a small molecule inhibitor of the mutagenic translesion synthesis pathway, nearly completely suppresses DENV infection in Vero E6 cells. This result suggests a novel link between dengue virus and the translesion synthesis pathway and highlights the therapeutic potential of JH-RE-06 for patients with acute dengue infection.Microbiology and Molecular GeneticsMaster of Science (MS
Exploring The Intersection Of Rev1 Inhibition And Autophagy: Implications For Cancer Radioresistance
No full textThe development of therapeutic resistance during cancer management remains a significant obstacle to ideal therapeutic outcomes. The ability of cancer cells to utilize the Translesion Synthesis (TLS) pathway to tolerate and bypass DNA damage induced by genotoxic therapy has been implicated as a mechanism for developing therapeutic resistance. TLS is a DNA damage bypass process that tolerates damage and contributes to mutagenesis, unlike the DNA repair pathway that fixes and repairs DNA damage. Mutagenesis is the cornerstone of cancer resistance to therapy, where newly mutagenized pathways perpetuate the survival of treated cells. As such, inhibition of TLS has garnered interest in solving the therapeutic resistance crisis. Small molecule inhibitors of REV1, a crucial TLS polymerase, effectively sensitize cancer cells to chemotherapy. First, using small molecule inhibitors of REV1 and mouse REV1 knockdown cell models, we delineated an extensive array of combination treatment modules of strand-breakage agents and REV1 inhibition. In this published work, we showed that despite the prevalence of double-strand breaks from ionizing radiation (IR) or etoposide treatment, the limitation of REV1 was cytoprotective to cells. We found that REV1 inhibition in IR-treated cells triggers an autophagy response with a cytoprotective effect and that REV1 polymerase is associated with a novel function of autophagy. In addition, we determined that autophagy inhibitors provided a narrow window of therapeutic sensitization. Second, we elucidated the mechanistic link between REV1, a TLS polymerase proposed to be involved in DNA damage bypass primarily in the nucleus, to its newly uncovered cytoplasmic functional regulation of autophagy. We employed high throughput RNA and proteomic analysis to capture gene and pathway enrichments to fully uncover all newer associations of REV1 with other cellular pathways specific to autophagy. Our results confirmed upregulation of the mTOR signaling pathway in REV1-inhibited cells, including associations with distinct energy metabolisms perturbations, such as engagement of glycolysis, endoplasmic stress responses, and unique DNA damage responses in the tested conditions. Mechanistically, REV1 inhibition activates the AMPK/mTOR signaling pathway, a coping mechanism for energy stress that activates autophagy. This pathway specifically relies on genotoxic stress, particularly activation of Chk1, which is known to activate the metabolic stress response with induction of autophagy as a coping mechanism. Further, by targeting the Chk1 signaling pathway through a commercial inhibitor, we rescued REV1-inhibition-induced autophagy, suggesting a significant leap in our understanding of new functional and synthetic lethal treatment model for cancer resistance. Collectively, this project uncovered new functional attributes of the DNA damage tolerance pathway via REV1 and its mechanistic implications. The results of this dissertation not only significantly add to our understanding of the cancer resistance problem, including clinical decision-making for cancer drug combinations, but most importantly, shed light on fundamental mechanisms of TLS-dependent genome instability programs.Cellular, Molecular and Biomedical SciencesDoctor of Philosophy (PhD
Site-Directed Mutagenesis of the REV1 BRCT Domain
No full textUndergraduateThe translesion synthesis (TLS) polymerase REV1 modulates error-prone replication of DNA and contains a BRCT domain that interacts with proliferating cell nuclear antigen (PCNA). Structural analysis has identified five amino acid residues within the BRCT domain that are critical to the BRCT-PCNA interaction. Site-directed mutagenesis was used to generate point mutants for the five amino acid residues and Sanger sequencing confirmed successful generation of the R68A, G76R, Y81A, and K86A point mutants. These point mutants provide a useful tool for investigating the in vitro significance of the BRCT-PCNA interaction on TLS
REV1 regulation of DNA damage response in the G2/M phase of the cell cycle
No full textGraduateThe S phase of the cell cycle engages in DNA replication. It’s prone to DNA damage from their deprotected nature, triggering DNA damage responses (DDRs). Typically, damage results in arrest, allowing the DDR pathway to engage in either repair or bypass damage to promote survival and integrity. For DNA damage bypass, low-fidelity polymerases orchestrate error-prone DNA synthesis, resulting in mutagenic nucleotide pairing. Here, REV1 is the principal scaffolding molecule that recruits other polymerases to the site of damage by protein-protein interactions. We hypothesized that REV1 may play an essential novel role in regulating the cell cycle
Novel small molecule inhibitors expose cancer therapeutic vulnerabilties
No full textUndergraduateCancer resistance to therapy remains the most challenging aspect of treatment and cure. Dysfunction in several critical cellular pathways causes resistance to chemotherapeutics. However, one common theme within the pathways causing cancer resistance is increased mutation formation. One major pathway for cancer cells to produce mutations is the Translesion Synthesis (TLS) process. TLS is a DNA damage bypass process, where specialized polymerases replicate over damaged DNA. Unrepaired DNA damage stalls replication, which is a cellular response to arrest the cell cycle and repair the damage. However, cancer cells utilize the same strategy by bypassing or replicating over DNA damages from the cancer drugs. Therefore, limiting translesion synthesis is an ideal strategy for suppressing cancer resistance
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Novel small molecule inhibitors expose cancer therapeutic vulnerabilties
No full textUndergraduateCancer resistance to therapy remains the most challenging aspect of treatment and cure. Dysfunction in several critical cellular pathways causes resistance to chemotherapeutics. However, one common theme within the pathways causing cancer resistance is increased mutation formation. One major pathway for cancer cells to produce mutations is the Translesion Synthesis (TLS) process. TLS is a DNA damage bypass process, where specialized polymerases replicate over damaged DNA. Unrepaired DNA damage stalls replication, which is a cellular response to arrest the cell cycle and repair the damage. However, cancer cells utilize the same strategy by bypassing or replicating over DNA damages from the cancer drugs. Therefore, limiting translesion synthesis is an ideal strategy for suppressing cancer resistance
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