Biochemistry, Biophysics, and Structural Biology Commons^™

Discovery Of A Small-Molecule Inhibitor That Traps Polθ On Dna And Synergizes With Parp Inhibitors, William Fried, Mrityunjay Tyagi, Leonid Minakhin, Gurushankar Chandramouly, Taylor Tredinnick, Mercy Ramanjulu, William Auerbacher, Marissa L Calbert, Timur Rusanov, Trung Hoang, Nikita Borisonnik, Robert Betsch, John Krais, Yifan Wang, Umeshkumar Vekariya, John Gordon, George Morton, Tatiana Kent, Tomasz Skorski, Neil Johnson, Wayne Childers, Xiaojiang Chen, Richard Pomerantz

Department of Biochemistry and Molecular Biology Faculty Papers

The DNA damage response (DDR) protein DNA Polymerase θ (Polθ) is synthetic lethal with homologous recombination (HR) factors and is therefore a promising drug target in BRCA1/2 mutant cancers. We discover an allosteric Polθ inhibitor (Polθi) class with 4-6 nM IC₅₀ that selectively kills HR-deficient cells and acts synergistically with PARP inhibitors (PARPi) in multiple genetic backgrounds. X-ray crystallography and biochemistry reveal that Polθi selectively inhibits Polθ polymerase (Polθ-pol) in the closed conformation on B-form DNA/DNA via an induced fit mechanism. In contrast, Polθi fails to inhibit Polθ-pol catalytic activity on A-form DNA/RNA in which the enzyme binds in …

Parp2 Promotes Break Induced Replication-Mediated Telomere Fragility In Response To Replication Stress, Daniela Muoio, Natalie Laspata, Rachel L Dannenberg, Caroline Curry, Simone Darkoa-Larbi, Mark Hedglin, Shikhar Uttam, Elise Fouquerel

Department of Biochemistry and Molecular Biology Faculty Papers

PARP2 is a DNA-dependent ADP-ribosyl transferase (ARTs) enzyme with Poly(ADP-ribosyl)ation activity that is triggered by DNA breaks. It plays a role in the Base Excision Repair pathway, where it has overlapping functions with PARP1. However, additional roles for PARP2 have emerged in the response of cells to replication stress. In this study, we demonstrate that PARP2 promotes replication stress-induced telomere fragility and prevents telomere loss following chronic induction of oxidative DNA lesions and BLM helicase depletion. Telomere fragility results from the activity of the break-induced replication pathway (BIR). During this process, PARP2 promotes DNA end resection, strand invasion and BIR-dependent …

Structural Basis For Dna Proofreading, Gina Buchel, Ashok Nayak, Karl Herbine, Azadeh Sarfallah, Viktoriia Sokolova, Angelica Zamudio-Ochoa, Dmitry Temiakov

Department of Biochemistry and Molecular Biology Faculty Papers

DNA polymerase (DNAP) can correct errors in DNA during replication by proofreading, a process critical for cell viability. However, the mechanism by which an erroneously incorporated base translocates from the polymerase to the exonuclease site and the corrected DNA terminus returns has remained elusive. Here, we present an ensemble of nine high-resolution structures representing human mitochondrial DNA polymerase Gamma, Polγ, captured during consecutive proofreading steps. The structures reveal key events, including mismatched base recognition, its dissociation from the polymerase site, forward translocation of DNAP, alterations in DNA trajectory, repositioning and refolding of elements for primer separation, DNAP backtracking, and displacement …

Rna World And The Development Of Rna Protocells, Benjamin C. Mayfield

PANDION: The Osprey Journal of Research and Ideas

Origins of life research, also known as pre-biotic chemistry or astrobiology, aims to unravel the mystery of the first cell’s origin on Earth. This interdisciplinary field encompasses biology, chemistry, and physics, with the primary goal of understanding the conditions necessary for life to emerge from abiotic environments. The RNA world hypothesis suggests that early life initially used RNA instead of DNA to store genomic information and for enzymatic functions. Protocells, membrane-bound entities with metabolic processes and self-replication capabilities, likely preceded the emergence of true cells. The challenges associated with RNA world is currently an active field of research. Advancements in …

Exploring The Interaction Of Minor-Groove-Binder Netropsin With Dna Using Optical Tweezers, Irbazhusain Shaikh

Honors Program Theses and Projects

Netropsin is an antibiotic that binds in the minor grooves of DNA, which also exhibits anticancer properties. There have been many previous studies that explored the binding of this drug to DNA using traditional methods where an ensemble averaging is used. In this study we explore the interaction of Netropsin with DNA at a single molecule level using dual beam optical tweezers. We trapped and stretched a single DNA molecule using optical tweezers to measure the force experienced by the DNA as a function of extension in the absence and presence of various concentrations of Netropsin. Our results show the …

Role Of Cdx4 And Sp5l In Zebrafish Development, Wesley Tsai

Honors Theses

The Caudal Type Homeobox transcription factors cdx are a family of genes found in vertebrates that regulates body regionalization and anterior-posterior patterning. They are also responsible for regulating axial elongation, but the mechanisms behind this behavior are not known. Previous studies in mouse embryonic stem cells have shown that the cdx genes are necessary for upregulating the gene sp5 which may be linked to axial elongation. Sp5 is a zinc-finger transcription factor belonging to the specificity protein (sp) family. Our group has used in-situ hybridization experiments on zebrafish embryos to show that sp5-like (sp5l) is transcribed within tailbud tissues that …

Sequence Selectivity In The Binding Of Melatonin To Phix174rf Dna, Camila Garcia

FIU Undergraduate Research Journal

Melatonin is an endogenous neurotransmitter that controls the circadian rhythm. When consumed through medication, it has been proven to serve as a treatment for sleep disorders and alleviate sleep quality. Stable levels of melatonin in the human organism are shown to be beneficial as it provides a protective layer to DNA strands ensuring their longevity; however, its excessive consumption may have damaging consequences on the long run. Here we present a study on the sequence selectivity in the binding of melatonin to DNA, intending to show that melatonin targets specific DNA sites. Binding tophiX174RF DNA was assayed using restriction enzyme …

Dpc29 Promotes Post-Initiation Mitochondrial Translation In Saccharomyces Cerevisiae, Kyle A. Hubble, Michael F. Henry

Rowan-Virtua School of Osteopathic Medicine Faculty Scholarship

Mitochondrial ribosomes synthesize essential components of the oxidative phosphorylation (OXPHOS) system in a tightly regulated process. In the yeast Saccharomyces cerevisiae, mitochondrial mRNAs require specific translational activators, which orchestrate protein synthesis by recognition of their target gene's 5'-untranslated region (UTR). Most of these yeast genes lack orthologues in mammals, and only one such gene-specific translational activator has been proposed in humans-TACO1. The mechanism by which TACO1 acts is unclear because mammalian mitochondrial mRNAs do not have significant 5'-UTRs, and therefore must promote translation by alternative mechanisms. In this study, we examined the role of the TACO1 orthologue in yeast. We …

Probing Amyloid-Beta Protein Structure And Dynamics With A Selective Antibody, Shikha Grover

Dissertations

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder. The AD brain is characterized by significant neuronal loss and accumulation of insoluble fibrillar amyloid-β protein (Aβ) plaques and tau protein neurofibrillary tangles in the brain. However, over the last decade, many studies have shown that the neurodegenerative effect of Aβ may in fact be caused by various soluble oligomeric forms as opposed to the insoluble fibrils. Furthermore, the data suggest that a pre-fibrillar aggregated form, termed protofibrils, mediates direct neurotoxicity, and triggers a robust neuroinflammatory response.

Antibodies targeting the various conformation of Aβ are important therapeutic agents to prevent the progression …

Impact Of Sample Conditions On Dna Phosphodiester Backbone Bi/Bii Conformational Equilibrium Dynamics, Autumn C. Pilarski

MSU Graduate Theses

DNA damage, such as single base lesions and mismatches, is highly prevalent within cells. If these DNA damage events are not repaired, they could lead to mutations and thus disease and cancer. Intricate repair mechanisms are in place to fix these damage events, one such being Base Excision Repair (BER) and associated enzyme: Thymine DNA Glycosylase (TDG). The first step of this repair process, recognition of the lesion by TDG, is not well understood. The following thesis presents results to better understand the fundamental biophysical question of how a DNA lesion within a mismatch context is recognized in a million …

Functional Characterization Of The Newly Discovered Type V Crispr-Cas Protein Cas12a2, Dylan J. Keiser

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Similarly to people, bacteria are under the treat of infection by viruses. To circumvent these threats, bacteria evolve complex immune systems. Our understanding of some of these immune systems has led to many advancements in the field of Biotechnology including tools that made expressing proteins for study in a lab easier, tools that revolutionized the feasibility of gene editing, and tools that could change the way we think about viral diagnostics and cancer therapeutics. A certain type of immune system that bacteria use to fight virus is called a CRISPR system. Presented here is work to understand the function of …

Expression And Purification Of E. Coli Yoaa, A Putative Helicase, Mark Gregory, Vincent Sutera Mr., Susan Lovett Dr.

Medical Student Research Symposium

All cells must maintain their genomic integrity to survive, which they achieve through several repair mechanisms that necessitate unwinding the damaged DNA by helicases. In Escherichia coli (E. coli), YoaA has been genetically shown to be involved in DNA repair and shares conserved sequences with helicase DinG. The goal of our study was to purify YoaA for further biochemical characterization. For expression, YoaA was fused to a His tag and overexpressed in MG1655 E.coli under the lacZ or T7 promoters for 2 hours, 4 hours, or overnight at 24oC, 30oC or 37oC. For purification, crude lysate was applied to a …

The Effects Of Crowding Agents On The Pka Of Physiologically Stable I-Motif Dna, Courtney Turner

Honors Theses

The overall goal of this thesis was to investigate the environmental conditions that induce i-Motif folding of the DNA strand DUX4L22, a cytosine-rich segment of DNA found in the human genome. Cellular conditions were simulated using sodium cacodylate buffer and multiple weights of polyethylene glycol as a crowding agent. The presence of i-motifs were confirmed by Circular Dichroism spectroscopy. I found that DUX4L22 does form i-motifs under these physiological simulations at both acidic and neutral pHs. DUX4L22 therefore shows potential for use in studies of a wide variety of biotechnological advances, such as regulatory switches in nanomachines or drug-delivery systems.

Bci Validation: Yfiler Plus Kit Validation, Chloe Koon

Honors Projects

In order to have access and use the Combined DNA Index System (CODIS), it is required by the Federal Bureau of Investigation's Quality Assurance Standards (FBI-QAS) for Forensic DNA Units to complete comprehensive validation studies on all equipment, materials, and methods used in the process of DNA analysis. This study continues validation previous done within the Ohio Bureau of Criminal Investigation (BCI). YFiler Plus is a DNA amplification kit that is used in cases where it is most useful to examine only male DNA profile(s) within a sample by amplifying loci only on the Y-Chromosome. Components of this study include …

Generating A Colorimetric Ssa4 Transcript Export Reporter For Multicopy Suppression Screen In S. Cerevisiae, Zaid Hatem

Belmont University Research Symposium (BURS)

The export of mRNA from the nucleus to the cytoplasm is a regulatory point that is essential to the pathway of gene expression in eukaryotic cells. The export of mRNA transcripts is mediated through selective doorways called the nuclear pore complexes (NPC). Additionally, there are proteins associated with the nuclear pore complex that assist in facilitating the export. This includes association with the export receptor, Mex67, which binds to the transcript and ferries it through NPCs. During cellular stress, such as heat shock, the export of housekeeping mRNA transcripts is halted, forcing these transcripts to remain inside the nucleus and …

Test-Driving The Next Generation Of Crispr Gene Editing, Olivia Gornichec, Kailey Mayer

Research on Capitol Hill

USU team Kailey, recent graduate of animal science, and Olivia, senior in biochemistry, have led and funded this project through a student grant. CRISPR has been making waves in the scientific community for its potential to help us edit genomes. However, that is just one of the known types of CRISPR, and other types aren’t in forms that are accessible to study. Kailey and Olivia have successfully cloned Type IV-B into a plasmid that can now be used to perform further research into what this system does. The two students never expected that, as undergrads, they would make a foundation-level …

Plants, Pipettes And Pcr, Elizabeth Vierling

Science and Engineering Saturday Seminars

Plants are amazing organisms that provide us with food, building materials, the pleasure of gardens, as well as providing the foundation of critical world ecosystems. Although they may look like they are just stuck in one place and doing not more than growing, they have many, many complex ways in which they respond to the environment. The goal of this STEM Ed session will be to discuss ways that plants can respond to the environment with hands on exercises and exploration of possible classroom activities. Participants will engage in state-of-the art methods of testing plant DNA composition using the polymerase …

Reproducibility Of Individual Dna Deposits Detected Through Cellular Fluorescence, Natalee Small-Davidson

Student Theses

Contact traces are an important part of DNA casework, but the probative value of any identified associations depends on the possibility of passive transfer. There is known individual variation in DNA left behind during contact, this DNA shedding propensity has an effect on whose DNA is detected. This study evaluated this variability using a cell staining approach. Volunteers were asked to deposit a fingerprint on a clean glass slide, then wash their hands and deposit a second fingerprint after a 30-minute wait without touching anything. Three sets of samples were collected over three consecutive weeks. Fingerprints were stained with a …

Investigating Factors That Affect Hiv-1 Capsid Stability, Max Mao, Joshua Temple

The Yale Undergraduate Research Journal

TKH HIV caSVLd, a SURWHLQ VKHOO cRPSRVHd RI PRQRPHULc XQLWV RI CA, IRUPV a IXOOHUHQH cRQH WKaW SURWHcWV HIV¶V YLUaO JHQRPH aQd enzymes during infection. I am interested in elucidating the factors that influence stability of the capsid shell and capturing the structural interactions between HIV capsid, host restriction factors, and small molecules using biochemical and structural biology techniques. HIV capsid shell was broken down and purified into hexamer and pentamer units for in vitro study. Structural assays were performed using X-ray crystallography and biochemical analysis was performed using pelleting assays. By understanding capsid structure with factors that confer stability, …

Type I Topoisomerases As Potential Targets For Therapeutics, Ahmed Seddek

FIU Electronic Theses and Dissertations

DNA topoisomerases are universal enzymes that control the topological features of DNA in all forms of life. This study aims to find potential inhibitors of some of the DNA topoisomerases in bacteria and humans that can be developed into potential therapeutics.

The first aim of this study is to find potential inhibitors of bacterial topoisomerase I that can be developed into antibiotics. There is an urgent need to develop novel antibiotics to overcome the world-wide health crisis of antimicrobial resistance. Virtual screening and biochemical assays were combined to screen thousands of compounds for potential inhibitors of bacterial topoisomerase I. NSC76027 …

Analysis Of Foki Cleavage Resistance Observed In Dna Sequences Generated Via The Combinatorial Selection Method, Repsa, Andre Berry

Master of Science in Chemical Sciences Theses

FokI is a thoroughly investigated and highly utilized restriction endonuclease that recognizes the DNA sequence, 5’-GGATG-3’, and cleaves outside of this site 9 and 13 base-pairs downstream. The shifted cleavage function possessed by this kind of endonuclease is utilized in many applications including the combinatorial selection method, REPSA. FokI employment in the REPSA procedure has demonstrated the tendency to select for an unmodified sequence that possesses the recognition site yet is refractory to cleavage by the enzyme. Sequencing of the cleavage resistant DNA has revealed the inhibitory event to be induced by the presence of an additional inversely oriented recognition …

Replication Protein A (Rpa) Targeting Of Uracil Dna Glycosylase (Ung2), Derek Chen, Brian P Weiser

Rowan-Virtua Research Day

Replication Protein A (RPA) is a single stranded DNA binding protein which stabilizes ssDNA for replication and repair. One function of RPA is to bind the DNA repair enzyme uracil DNA glycosylase (UNG2) and direct its activity towards ssDNA dsDNA junctions.

UNG2 removes uracil bases from DNA which can appear through dUMP misincorporation or through cytosine deamination. If uracil is present instead of a cytosine, then the original GC pair becomes a GU pair. The uracil will then base pair to adenine in the replicated daughter strand. This results in a GC → AT mutation that could contribute to cancer …

Chemical And Co-Solute Effects Of Polyethylene Glycol On I-Motif Formation, Lindsey Rutherford

Honors Theses

DNA typically forms Watson and Crick double helix structures in which adenine, thymine, guanine, and cytosine pair with their complimentary DNA base. However, DNA i-motif structures can form in cytosine rich DNA, typically under slightly acidic conditions (~pH 6). DNA i-motifs are four stranded secondary structures in which cytosine pairs with cytosine to form a quadruplex. The i-motifs are typically formed in acidic conditions because of the protonation in the C•C base pair between one of the three hydrogen bases. Recent studies have suggested i-motifs can also form under neutral conditions, which is more realistic for a cell. It is …

Effects Of Crowding Agents On I-Motif Dna, Hayden Brines

Honors Theses

Deoxyribonucleic acid (DNA) is a well-known double stranded, helical, biological molecule. In addition to its more commonly known structure, DNA can also form more complicated structures like G-quadruplexes and i-motifs (iM). The iMs are formed by cytosine rich DNA and are a four stranded structure that is typically looped around itself. The iM formation is typically pH-dependent and is favored in more acidic conditions; the pKa value is approximately 6.5. This pKa value allows for potential in vivo formation, since the cells have a pH of approximately 7.3. Due to this, iMs are thought to be powerful, innovative molecules for …

Nucleic Acids Promote Oligomerization Of Immunoglobulin G, Alexa Gomez

Electronic Theses and Dissertations

Nucleic acids have been found to prevent aggregation as chaperones, as well as act as co-factors and promote aggregation of amyloidogenic proteins leading to various diseases. Immunoglobulin G, IgG, are prone to aggregate as therapeutic proteins, and light chains of IgG can form amyloid fibrils, causing a disease known as light chain amyloidosis. Here we discuss the effect nucleic acids have on full-length immunoglobulin G aggregation. Our results show G-quadruplex DNA, and bulk DNA lead to oligomerization of full-length IgG, and induce increases in secondary structure. Tryptophan fluorescence indicates structural changes are occurring in the presence of DNA. Additionally, IgG …

Quantifying Anticancer Drug Doxorubicin Binding To Dna Using Optical Tweezers, Zachary Ells

Honors Program Theses and Projects

Doxorubicin is a successful anticancer drug approved for use in the 1970s and is considered to be one of the most effective cancer treatment methods today. Although Doxorubicin has positive survival statistics it has very negative side effects in many cases. Bleeding from the soles of the palms and feet, along with excruciating pain is often exhibited through the administration of this drug. Based on the preliminary findings utilizing optical tweezers we anticipate that this study will provide critical information about the drug binding mechanism. Single molecule biophysics techniques have provided useful insight into the DNA-binding mechanisms of small molecules. …

Structural Characterization And Selective Drug Targeting Of Higher-Order Dna G-Quadruplex Systems., Robert Chandos Monsen

Electronic Theses and Dissertations

There is now substantial evidence that guanine-rich regions of DNA form non-B DNA structures known as G-quadruplexes in cells. G-quadruplexes (G4s) are tetraplex DNA structures that form amid four runs of guanines which are stabilized via Hoogsteen hydrogen bonding to form stacked tetrads. DNA G4s have roles in key genomic functions such as regulating gene expression, replication, and telomere homeostasis. Because of their apparent role in disease, G4s are now viewed as important molecular targets for anticancer therapeutics. To date, the structures of many important G4 systems have been solved by NMR or X-ray crystallographic techniques. Small molecules developed to …

Additive Modulation Of Dna-Dna Interactions By Interstitial Ions, Wei Meng, Raju Timsina, Abby Bull, Kurt Andresen, Xiangyun Qiu

Physics and Astronomy Faculty Publications

Quantitative understanding of biomolecular electrostatics, particularly involving multivalent ions and highly charged surfaces, remains lacking. Ion-modulated interactions between nucleic acids provide a model system in which electrostatics plays a dominant role. Using ordered DNA arrays neutralized by spherical cobalt3+ hexammine and Mg2+ ions, we investigate how the interstitial ions modulate DNA-DNA interactions. Using methods of ion counting, osmotic stress, and x-ray diffraction, we systematically determine thermodynamic quantities, including ion chemical potentials, ion partition, DNA osmotic pressure and force, and DNA-DNA spacing. Analyses of the multidimensional data provide quantitative insights into their interdependencies. The key finding of this study is that …

Toxicity Analysis Of 2’-Deoxyguanosine-N2-6-Aminopyrene And 2’-Deoxyguanosine-N2-8-Aminopyrene In Escherichia Coli, Emily Janeiro

Honors Scholar Theses

Cancer is a disease that stems from genomic errors that are not corrected properly by cellular repair mechanisms. Errors are more likely to form when organisms are subjected to DNA damage by mutagenic compounds. 1-Nitropyrene, a nitrated polycyclic aromatic hydrocarbon (nitro-PAH), has been shown to be a potent mutagen that causes cancer. Nitro-PAHs can arise from diesel exhaust products in the environment. Out of all nitro-PAHs, 1-nitropyrene is found in largest quantities in the environment. This poses a great need to study its effects biochemically in order to address its toxicity in DNA. Other nitropyrene derivatives, including 1,6-dinitropyrene and 1,8-dinitropyrene, …

Diversity Of The Major Histocompatibility Complex In African Penguins (Spheniscus Demersus) In Situ, Athena Schalk

Undergraduate Honors Thesis Projects

The Major Histocompatibility Complex (MHC) is responsible for the immune response in all jawed vertebrates and protects individuals against a variety of pathogens and diseases. Maintaining genetic diversity within the MHC exons is critical to protecting endangered species. African penguins (Spheniscus demersus) are in danger of losing their MHC diversity in isolated populations due to reductions in population size associated with environmental changes and human activity. This study analyzes the diversity within the exons in the DNA encoding the MHC by amplifying the exons through polymerase chain reaction and identifying alleles through denaturing gradient gel electrophoresis. Wild populations of …