Publications by authors named "Stefanie H Chen"

In the age of an ongoing pandemic and the ungrading movement, many instructors have been taking a closer look at their assessment methods. Assessment in science courses typically focuses heavily on checking understanding of underlying vocabulary and processes rather than highlighting an emotional connection to the material. For the final exam in a senior-level virus biotechnology course in Spring 2021, Fall 2021, and Spring 2022, an additional assessment question asking students what they found beautiful about viruses was implemented.

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The COVID-19 pandemic forced many courses to move online, presenting a particular challenge for hands-on laboratory courses. One such course in our Biotechnology track is an advanced Protein Interactions lecture/laboratory course. This 8-week course typically meets for 5 h a week in the laboratory space.

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The accelerating expansion of online bioinformatics tools has profoundly impacted molecular biology, with such tools becoming integral to the modern life sciences. As a result, molecular biology laboratory education must train students to leverage bioinformatics in meaningful ways to be prepared for a spectrum of careers. Institutions of higher learning can benefit from a flexible and dynamic instructional paradigm that blends up-to-date bioinformatics training with best practices in molecular biology laboratory pedagogy.

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The rapid development of molecular biotechnology presents a curricular challenge for educators trying to provide students with relevant coursework. A comprehensive biology education should also include opportunities for students to develop intellectual and technical skills through authentic research experiences. Integrating relevant and interesting research projects into their classes, however, can be a challenging task for instructors.

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DNA lesions or other barriers frequently compromise replisome progress. The SF2 helicase RecG is a key enzyme in the processing of postreplication gaps or regressed forks in Escherichia coli. A deletion of the recG gene renders cells highly sensitive to a range of DNA damaging agents.

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Proteins must interact with a variety of other cellular components to properly perform their functions. We have developed a series of five experiments based on the robust bacterial single-stranded DNA binding protein (SSB) to characterize both known and unknown protein-protein and protein-DNA interactions. Students work in groups to generate and process data from electrophoretic mobility shift assays (EMSA), yeast two-hybrid, far Western, chromatin immunoprecipitation (ChIP), and fluorescence microscopy experiments, including choosing a novel condition for each.

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When replication forks encounter template DNA lesions, the lesion is simply skipped in some cases. The resulting lesion-containing gap must be converted to duplex DNA to permit repair. Some gap filling occurs via template switching, a process that generates recombination-like branched DNA intermediates.

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Many studies confirm the benefit of active learning in STEM teaching. However, many faculty have been slow to adopt such practices, perhaps due to limited time to learn and implement new approaches. One way to address this deficit is to offer structured teaching postdoctoral experiences to trained scientists who want to enter academia.

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On May 22, 2017, administrative law Judge Leslie Rogall of the Department of Health and Human Services' Departmental Appeals Board, Civil Remedies Division, ruled in favor of the Office of Research Integrity (ORI) concerning its decision to charge former University of California at Riverside biochemistry professor Frank Sauer with research misconduct for fabricating or falsifying digital image data included in three papers and seven grant applications submitted to the National Institutes of Health. More specifically, Sauer was deemed responsible for manipulating, reusing, and falsely labeling images of autoradiograms and gels in his research in epigenetics. One month after this decision, ORI announced its final ruling concerning Sauer, which barred him from serving in any advisory capacity to the Public Health Services and required him to retract affected papers.

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The bacterial single-stranded DNA binding protein (SSB) acts as an organizer of DNA repair complexes. The radD gene was recently identified as having an unspecified role in repair of radiation damage and, more specifically, DNA double-strand breaks. Purified RadD protein displays a DNA-independent ATPase activity.

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The UvrD helicase has been implicated in the disassembly of RecA nucleoprotein filaments in vivo and in vitro. We demonstrate that UvrD utilizes an active mechanism to remove RecA from the DNA. Efficient RecA removal depends on the availability of DNA binding sites for UvrD and/or the accessibility of the RecA filament ends.

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A transposon insertion screen implicated the yejH gene in the repair of ionizing radiation-induced damage. The yejH gene, which exhibits significant homology to the human transcription-coupled DNA repair gene XPB, is involved in the repair of double-strand DNA breaks. Deletion of yejH significantly sensitized cells to agents that cause double-strand breaks (ionizing radiation, UV radiation, ciprofloxacin).

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To further an improved understanding of the mechanisms used by bacterial cells to survive extreme exposure to ionizing radiation (IR), we broadly screened nonessential Escherichia coli genes for those involved in IR resistance by using transposon-directed insertion sequencing (TraDIS). Forty-six genes were identified, most of which become essential upon heavy IR exposure. Most of these were subjected to direct validation.

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Although Blm and Top3α are known to form a minimal dissolvasome that can uniquely undo a double Holliday junction structure, the details of the mechanism remain unknown. It was originally suggested that Blm acts first to create a hemicatenane structure from branch migration of the junctions, followed by Top3α performing strand passage to decatenate the interlocking single strands. Recent evidence suggests that Top3α may also be important for assisting in the migration of the junctions.

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DNA topoisomerases are nature's tools for resolving the unique problems of DNA entanglement that occur owing to unwinding and rewinding of the DNA helix during replication, transcription, recombination, repair, and chromatin remodeling. These enzymes perform topological transformations by providing a transient DNA break, formed by a covalent adduct with the enzyme, through which strand passage can occur. The active site tyrosine is responsible for initiating two transesterifications to cleave and then religate the DNA backbone.

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Previously, we published a method for creating a novel DNA substrate, the double Holliday junction substrate. This substrate contains two Holliday junctions that are mobile, topologically constrained and separated by a distance comparable with conversion tract lengths. Although useful for studying late stage homologous recombination in vitro, construction of the substrate requires significant effort.

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Topoisomerase IIIα (Top3α) is an essential component of the double Holliday junction (dHJ) dissolvasome complex in metazoans, along with Blm and Rmi1/2. This important anti-recombinogenic function cannot be performed by Top3β, the other type IA topoisomerase present in metazoans. The two share a catalytic core but diverge in their tail regions.

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