Transfer Of Genetic Information Research Articles

Characterization of Non-selected Intermolecular Gene Conversion in the Polyploid Haloarchaeon Haloferax volcanii.

Gene conversion is defined as the non-reciprocal transfer of genetic information from one site to a homologous, but not identical site of the genome. In prokaryotes, gene conversion can increase the variance of sequences, like in antigenic variation, but can also lead to a homogenization of sequences, like in the concerted evolution of multigene families. In contrast to these intramolecular mechanisms, the intermolecular gene conversion in polyploid prokaryotes, which leads to the equalization of the multiple genome copies, has hardly been studied. We have previously shown the intermolecular gene conversion in halophilic and methanogenic archaea is so efficient that it can be studied without selecting for conversion events. Here, we have established an approach to characterize unselected intermolecular gene conversion in Haloferax volcanii making use of two genes that encode enzymes involved in carotenoid biosynthesis. Heterozygous strains were generated by protoplast fusion, and gene conversion was quantified by phenotype analysis or/and PCR. It was verified that unselected gene conversion is extremely efficient and it was shown that gene conversion tracts are much longer than in antigenic variation or concerted evolution in bacteria. Two sites were nearly always co-converted when they were 600 bp apart, and more than 30% co-conversion even occurred when two sites were 5 kbp apart. The gene conversion frequency was independent from the extent of genome differences, and even a one nucleotide difference triggered conversion.

Commodification of the living: regulatory problems of commercialization of biomaterials in the process of development of genomics

This article explores the normative problems of commodification of biomaterials in the process of development of genomics and genome medicine. It is demonstrated that in the era of advanced biocapitalism, when the relations between capital, knowledge and life become of particular importance, biomaterials undergo an economic turnover, are viewed as the objects of property and patent law, becoming the source of gaining profit. This results in the conflicts associated with the protection of rights of the individual, whose body is the source of biomaterials. In the context of consideration of the practices of commodification of biomaterials, the author reviews different modes of relations between the individual, science and society, with the characteristic to each of them articulation of the priority of personal or public good. The article provides the ethical analysis of incidents caused by the development of genetic technologies within the framework of the mode of confrontation between the individual and science, altruistic and compensatory modes, and mode of protection of civil rights. The conclusion is made that the developing processes of commodification require finding balance between the rights of the state and the interests of individuals, public good and personal values. The right to control own biomaterials and genetic information, voluntary and free transfer of biological materials, observance of biosafety and medical confidentiality – all these problems of the development of genomics require constant ethical monitoring in each specific case of using biomaterials.

An Insight on the Role of Altered Function and Expression of Exosomes and MicroRNAs in Female Reproductive Diseases.

Exosomes are small bilayer-lipid membrane vesicles secreted by living cells that are able to transfer regulatory molecules and genetic information from one cell to another. These vesicles are enriched with several nucleic acids including mRNAs, microRNAs (miRNAs), other non-coding RNAs, as well as proteins and lipids. Alterations in the exosomal content and functions are observed in numerous reproductive diseases in both animals and human cases. MicroRNAs, a class of small endogenous RNA molecules, can negatively regulate gene expression at the post-transcription level. Aberrant microRNA expression has been reported in multiple human reproductive diseases such as polycystic ovary syndrome, preeclampsia, uterine leiomyomata, ovarian cancer, endometriosis, and Asherman's syndrome. This study focuses to review recent research on alterations of microRNA expression and the role of exosomes in female reproductive diseases. It has been demonstrated that exosomes may be a potential therapeutic approach in various female reproductive diseases. In addition, changes in expression of microRNAs act as molecular biomarkers for diagnosis of several reproductive diseases in women, and regulation of their expression can potentially reduce infertility.

Design of Abiological Digital Poly(phosphodiester)s.

In biological systems, the storage and transfer of genetic information rely on sequence-controlled nucleic acids such as DNA and RNA. It has been realized for quite some time that this property is not only crucial for life but could also be very useful in human applications. For instance, DNA has been actively investigated as a digital storage medium over the past decade. Indeed, the "hard-disk of life" is an obvious choice and a highly optimized material for storing data. Through decades of nucleic acids research, technological tools for parallel synthesis and sequencing of DNA have been readily available. Consequently, it has already been demonstrated that different types of documents (e.g., texts, images, videos, and industrial data) can be stored in chemically synthesized DNA libraries. However, DNA is subject to biological constraints, and its molecular structure cannot be easily varied to match technological needs. In fact, DNA is not the only macromolecule that enables data storage. In recent years, it has been demonstrated that a wide variety of synthetic polymers can also be used for such a purpose. Indeed, modern polymer synthesis allows the preparation of synthetic macromolecules with precisely controlled monomer sequences. Altogether, about a dozens of synthetic digital polymers have already been described, and many more can be foreseen. Among them, sequence-defined poly(phosphodiester)s are one of the most promising options. These polymers are prepared by stepwise phosphoramidite chemistry like chemically synthesized oligonucleotides. However, they are constructed with non-natural building blocks and therefore share almost no structural characteristics with nucleic acids, except phosphate repeat units. Still, they contain readable digital messages that can be deciphered by nanopore sequencing or mass spectrometry sequencing. In this Account, we describe our recent research efforts in synthesizing and sequencing optimal abiological digital poly(phosphodiester)s. A major advantage of these polymers over DNA is that their molecular structure can easily be varied to tune their properties. During the last 5 years, we have engineered the molecular structure of these polymers to adjust crucial parameters such as the storage density, storage capacity, erasability, and readability. Consequently, high-capacity PPDE chains, containing hundreds of bits per chains, can now be synthesized and efficiently sequenced using a routine mass spectrometer. Furthermore, sequencing data can be automatically decrypted with the help of decoding software. This new type of coded matter can also be edited using practical physical triggers such as light and organized in space by programmed self-assembly. All of these recent improvements are summarized and discussed herein.

DNA Manipulation and Single-Molecule Imaging.

DNA replication, repair, and recombination in the cell play a significant role in the regulation of the inheritance, maintenance, and transfer of genetic information. To elucidate the biomolecular mechanism in the cell, some molecular models of DNA replication, repair, and recombination have been proposed. These biological studies have been conducted using bulk assays, such as gel electrophoresis. Because in bulk assays, several millions of biomolecules are subjected to analysis, the results of the biological analysis only reveal the average behavior of a large number of biomolecules. Therefore, revealing the elementary biological processes of a protein acting on DNA (e.g., the binding of protein to DNA, DNA synthesis, the pause of DNA synthesis, and the release of protein from DNA) is difficult. Single-molecule imaging allows the analysis of the dynamic behaviors of individual biomolecules that are hidden during bulk experiments. Thus, the methods for single-molecule imaging have provided new insights into almost all of the aspects of the elementary processes of DNA replication, repair, and recombination. However, in an aqueous solution, DNA molecules are in a randomly coiled state. Thus, the manipulation of the physical form of the single DNA molecules is important. In this review, we provide an overview of the unique studies on DNA manipulation and single-molecule imaging to analyze the dynamic interaction between DNA and protein.

The S. pombe CDK5 Orthologue Pef1 Cooperates with Three Cyclins, Clg1, Pas1 and Psl1, to Promote Pre-Meiotic DNA Replication.

Meiosis is a specialized cell division process that mediates genetic information transfer to the next generation. Meiotic chromosomal segregation occurs when DNA replication is completed during the pre-meiotic S phase. Here, we show that Schizosaccharomyces pombe Pef1, an orthologue of mammalian cyclin-dependent kinase 5 (CDK5), is required to promote pre-meiotic DNA replication. We examined the efficiency of meiotic initiation using pat1-114 mutants and found that, meiotic nuclear divisions did not occur in the pef1Δ pat1-114 strain. Deletion of pef1 also suppressed the expression of DNA replication factors and the phosphorylation of Cdc2 Tyr-15. The double deletion of clg1 and psl1 arrested meiotic initiation in pat1-114 mutant cells, similar to that of pef1-deficient cells. Meiotic progression was also slightly delayed in the pas1-deficient strain. Our results reveal that Pef1 regulates cyclin-coordinated meiotic progression.

The role of the DFF40/CAD endonuclease in genomic stability.

Maintenance of genomic stability in cells is primordial for cellular integrity and protection against tumor progression. Many factors such as ultraviolet light, oxidative stress, exposure to chemical reagents, particularly mutagens and radiation, can alter the integrity of the genome. Thus, human cells are equipped with many mechanisms that prevent these irreversible lesions in the genome, as DNA repair pathways, cell cycle checkpoints, and telomeric function. These mechanisms activate cellular apoptosis to maintain DNA stability. Emerging studies have proposed a new protein in the maintenance of genomic stability: the DNA fragmentation factor (DFF). The DFF40 is an endonuclease responsible of the oligonucleosomal fragmentation of the DNA during apoptosis. The lack of DFF in renal carcinoma cells induces apoptosis without oligonucleosomal fragmentation, which poses a threat to genetic information transfer between cancerous and healthy cells. In this review, we expose the link between the DFF and genomic instability as the source of disease development.

Interaction of hydrogen peroxide molecules with non-specific DNA recognition sites

Ion beam therapy is one of the most progressive methods in cancer treatment. Studies of the water radiolysis process show that the most long-living species that occur in the medium of a biological cell under the action of ionizing irradiation are hydrogen peroxide (H$_2$O$_2$) molecules. But the role of H$_2$O$_2$ molecules in the DNA deactivation of cancer cells in ion beam therapy has not been determined yet. In the present paper, the competitive interaction of hydrogen peroxide and water molecules with atomic groups of non-specific DNA recognition sites (phosphate groups PO$_4$) is investigated. The interaction energies and optimized spatial configurations of the considered molecular complexes are calculated with the help of molecular mechanics method and quantum chemistry approach. The results show that the H$_2$O$_2$ molecule can form a complex with the PO$_4$ group (with and without a sodium counterion) that is more energetically stable than the same complex with the water molecule. Formation of such complexes can block genetic information transfer processes in cancer cells and can be an important factor during ion beam therapy treatment.

Trophoblast Stem-Cell-Derived Exosomes Improve Doxorubicin-Induced Dilated Cardiomyopathy by Modulating the let-7i/YAP Pathway

Trophoblast stem cells (TSCs) have been confirmed to play a cardioprotective role in heart failure. However, whether TSC-derived exosomes (TSC-exos) can protect against cardiac injury remains unclear. In the present study, TSC-exos were isolated from the supernatant of TSCs using the ultracentrifugation method and characterized by transmission electron microscopy and western blotting. Utilizing the public Gene Expression Omnibus (GEO) database, we found that let-7i and Yes-associated protein 1 (YAP) could participate in the development of heart failure. In vitro, AC16 cardiomyocytes subjected to doxorubicin (DOX) were treated with TSC-exos or let-7i mimic. Flow cytometry showed that TSC-exos and let-7i both decreased cardiomyocyte apoptosis. In vivo, mice that were intraperitoneally injected into DOX received either PBS, TSC-exos, or AAV9-let7iup for let-7i overexpression. Mice receiving TSC-exos and AAV9-let7iup showed improved cardiac function and decreased inflammatory responses, accompanied by downregulated YAP signaling. Mechanistically, TSC-exos could transfer let-7i to cardiomyocytes and silence the YAP signaling pathway. In conclusion, TSC-exos could alleviate DOX-induced cardiac injury via the let-7i/YAP pathway, which sheds new light on the application of TSC-exos as a potential therapeutic tool for heart failure.

Pollen-mediated gene flow and transfer of resistance alleles from herbicide-resistant broadleaf weeds

AbstractPollen-mediated gene flow (PMGF) refers to the transfer of genetic information (alleles) from one plant to another compatible plant. With the evolution of herbicide-resistant (HR) weeds, PMGF plays an important role in the transfer of resistance alleles from HR to susceptible weeds; however, little attention is given to this topic. The objective of this work was to review reproductive biology, PMGF studies, and interspecific hybridization, as well as potential for herbicide resistance alleles to transfer in the economically important broadleaf weeds including common lambsquarters, giant ragweed, horseweed, kochia, Palmer amaranth, and waterhemp. The PMGF studies involving these species reveal that transfer of herbicide resistance alleles routinely occurs under field conditions and is influenced by several factors, such as reproductive biology, environment, and production practices. Interspecific hybridization studies withinAmaranthusandAmbrosiaspp. show that herbicide resistance allele transfer is possible between species of the same genus but at relatively low levels. The widespread occurrence of HR weed populations and high genetic diversity is at least partly due to PMGF, particularly in dioecious species such as Palmer amaranth and waterhemp compared with monoecious species such as common lambsquarters and horseweed. Prolific pollen production in giant ragweed contributes to PMGF. Kochia, a wind-pollinated species can efficiently disseminate herbicide resistance alleles via both PMGF and tumbleweed seed dispersal, resulting in widespread occurrence of multiple HR kochia populations. The findings from this review verify that intra- and interspecific gene flow can occur and, even at a low rate, could contribute to the rapid spread of herbicide resistance alleles. More research is needed to determine the role of PMGF in transferring multiple herbicide resistance alleles at the landscape level.

Harnessing DNA Replication Stress for Novel Cancer Therapy.

DNA replication is the fundamental process for accurate duplication and transfer of genetic information. Its fidelity is under constant stress from endogenous and exogenous factors which can cause perturbations that lead to DNA damage and defective replication. This can compromise genomic stability and integrity. Genomic instability is considered as one of the hallmarks of cancer. In normal cells, various checkpoints could either activate DNA repair or induce cell death/senescence. Cancer cells on the other hand potentiate DNA replicative stress, due to defective DNA damage repair mechanism and unchecked growth signaling. Though replicative stress can lead to mutagenesis and tumorigenesis, it can be harnessed paradoxically for cancer treatment. Herein, we review the mechanism and rationale to exploit replication stress for cancer therapy. We discuss both established and new approaches targeting DNA replication stress including chemotherapy, radiation, and small molecule inhibitors targeting pathways including ATR, Chk1, PARP, WEE1, MELK, NAE, TLK etc. Finally, we review combination treatments, biomarkers, and we suggest potential novel methods to target DNA replication stress to treat cancer.

MiR-124a Regulates Extracellular Vesicle Release by Targeting GTPase Rabs in Lung Cancer.

Lung cancer is the leading cause of cancer mortality worldwide. Increased understanding of the molecular mechanisms of the disease has led to the development of novel therapies and improving outcomes. Recently, extracellular vesicles (EVs) have emerged as vehicles for the transfer of genetic information between tumors and their microenvironment and have been implicated in lung cancer initiation, progression, and response to therapy. However, the mechanisms that drive the biogenesis and selective packaging of EVs remain poorly understood. Rab family guanosine triphosphates (GTPases) and their regulators are important membrane trafficking organizers. In this study, we investigated the role of select Rab GTPases on the regulation of EV release. We found that microRNAs target Rab GTPases to regulate EV release from lung cancer cell lines. In particular, Rab32 is a target of miR-124a, and siRNA and miRNA mediated inhibition of Rab32 leads to impaired EV secretion. The downstream implications for microRNA-based regulation of EV release are currently under investigation.

Vector genetics, insecticide resistance and gene drives: An agent-based modeling approach to evaluate malaria transmission and elimination.

Vector control has been a key component in the fight against malaria for decades, and chemical insecticides are critical to the success of vector control programs worldwide. However, increasing resistance to insecticides threatens to undermine these efforts. Understanding the evolution and propagation of resistance is thus imperative to mitigating loss of intervention effectiveness. Additionally, accelerated research and development of new tools that can be deployed alongside existing vector control strategies is key to eradicating malaria in the near future. Methods such as gene drives that aim to genetically modify large mosquito populations in the wild to either render them refractory to malaria or impair their reproduction may prove invaluable tools. Mathematical models of gene flow in populations, which is the transfer of genetic information from one population to another through migration, can offer invaluable insight into the behavior and potential impact of gene drives as well as the spread of insecticide resistance in the wild. Here, we present the first multi-locus, agent-based model of vector genetics that accounts for mutations and a many-to-many mapping cardinality of genotypes to phenotypes to investigate gene flow, and the propagation of gene drives in Anopheline populations. This model is embedded within a large scale individual-based model of malaria transmission representative of a high burden, high transmission setting characteristic of the Sahel. Results are presented for the selection of insecticide-resistant vectors and the spread of resistance through repeated deployment of insecticide treated nets (ITNs), in addition to scenarios where gene drives act in concert with existing vector control tools such as ITNs. The roles of seasonality, spatial distribution of vector habitat and feed sites, and existing vector control in propagating alleles that confer phenotypic traits via gene drives that result in reduced transmission are explored. The ability to model a spectrum of vector species with different genotypes and phenotypes in the context of malaria transmission allows us to test deployment strategies for existing interventions that reduce the deleterious effects of resistance and allows exploration of the impact of new tools being proposed or developed.

Effect of artificial insemination and natural mating on reproductive parameters in pigs of warm-humid climate region

Artificial insemination is a popular assisted reproductive technology that ensures transfer of genetic information from animal to animal. This study was meant to evaluate the influence of artificial insemination and natural mating on selected reproductive parameters. Five hybrid females of Duroc-landrace line were selected while 3 boars were used for the mating. Fresh semen was collected from 2 hybrid boars of Yorkshire-Landrace and Yorkshire-Pietrain line and the third boar - a Durocbreed (control) was used to stimulate the sows into oestrus and mate them naturally. Landrace-Yorkshire had shorter time for semen release than Pietrain-Yorkshire breed at first and second time of collecting the semen. Similarly, live born piglets of artificial insemination served 24% higher than natural mating. Therefore, a well-timed artificial insemination method using fresh semen would improve the number of piglets at parturition.

Zinc detection in cosmetics

Zinc is a metal which participates in the control of genetic information transfer, protein biosynthesis, affects the proper structure of the skin and hair, has bactericidal activity, accelerates wound healing, increases resistance to infection. It has an effect on skin regeneration and affects collagen metabolism.The aim of the study was to check it zinc is present in cosmetics.To detect zinc in cosmetics, 0.2 g were weighed into a 25 cm3 beaker. 5 cm3 of an 80% acetic acid solution was added, the beaker was covered with a watch glass and the contents were heated for 5 minutes. The suspension was cooled, poured into a centrifuge tube and centrifuged. The supernatant liquid was poured onto a watch glass, a few drops of Na2S solution were added. The precipitation of the white ZnS precipitate indicated the presence of zinc in the sample.105 samples of cosmetics were collected. The compositions of these cosmetics were analyzed.Zinc and its compounds were enumerated by the manufacturers in the composition of 14 cosmetics collected for the study. Presence of zinc was confirmed in Bell HYPOAllergenic - Powder, Face palette Bronze'n'blush no 14 and 24, Skin79 Super + Beblesh Balm, MaxFactor - Powder, My Secret - eye shadow, Paese - eye shadow , Ziaja med - soothing treatment, Ziaja GdanSkin - hydrogel face, Tołpa dermo face mask, Mixa - Against imperfections mask, The Ordinary serum, Oriflame Royal Velvet - night cream and BeBeauty Care - face mask.Conclusion: Zinc was detected in 14 cosmetics.

Abstract B062: Kaiso influences immune signaling of breast cancer exosomes

Abstract Introduction: Exosomes are communication vesicles act as mediator of intracellular transfer of genetic information, act an important role in intercommunication between tumor cells and immune cells. However, the mechanism underlining this cell-cell communication is not well understanding, particularly in African American breast cancer patients. Recently, our lab has demonstrated that Kaiso, a novel bi-modal transcription factor is highly expressed in African American breast cancer and notably, high Kaiso expression correlates with breast cancer aggressiveness and the disparity in survival outcomes of breast cancer patients of African American compared to European American patients. However, the differential expression and biological consequences of Kaiso in immune signaling of breast cancer exosomes has not been studied yet. Herein we demonstrate the biological role of Kaiso in immune signaling in breast cancer exosomes. Methods: In this study we utilized Nanostring immune profiling technology along with multiple in vitro and in vivo assays were used to study the role of Kaiso in breast cancer immune escape. Results: Nanostring pan cancer immune profiling demonstrated that European American breast cancer exosomes exhibited higher expression of TILs markers, T cell activation markers and CD8+T Cells markers compared to African American, while we observed an increase in the expression of the anti-phagocytic molecule CD47 in breast cancer patient exosomes of African American compared to European American patients. In addition to that CD47 and SIRP-α (Signal Regulatory Protein) are highly expressed in Kaiso-scrambled MDA-MB-231 cells (sh-Scr) and exosomes, whereas THBS1, which is a regulator of CD47 expression and is regarded as angiogenesis inhibitor is significantly increased in sh-Kaiso MDA-231 cells and exosomes. Additionally, we observed that Kaiso directly binds methylated sequences in the promoter region of CD47 and THBS1 by ChIP assay. Furthermore, in vivo sh-Kaiso cells injected into athymic mice exhibited delayed tumor formation after four weeks with smaller tumor size as compared to sh-SCR cells, and we observed higher expression of THBS1 with lower expression of CD47 and SIRP-α molecules by IHC and exosomes isolated from invivo tumors, indicating that Kaiso is associated with macrophage mediated immune escape. Conclusion: These findings demonstrate the important role of kaiso in immune signaling through exosomes which may be related with more aggressive cancer phenotype in breast cancer specially in African Americans. Citation Format: Shakir U Ahmed, Brittany Davis, Benjamin Adu Addai, Balasubramanyanam Karanam, Melissa Davis, William Grizzle, Honghe Wang, Clayton C Yates. Kaiso influences immune signaling of breast cancer exosomes [abstract]. In: Proceedings of the Twelfth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2019 Sep 20-23; San Francisco, CA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(6 Suppl_2):Abstract nr B062.

Effect of Kaiso on immune signaling of breast cancer exosomes.

3088 Background: Exosomes are communication vesicles that act as mediators of intracellular transfer of genetic information, an important role in intercommunication between tumor cells and immune cells. However, the mechanism underlining this cell-cell communication is not well understanding, particularly in African American breast cancer patients. Recently, our lab has demonstrated that Kaiso, a novel bi-modal transcription factor is highly expressed in African American breast cancer and notably, high Kaiso expression correlates with breast cancer aggressiveness and the disparity in survival outcomes of breast cancer patients of African American compared to European American patients. However, the differential expression and biological consequences of Kaiso in immune signaling of breast cancer exosomes has not been studied yet. Herein we demonstrate the biological role of Kaiso in immune signaling in breast cancer exosomes. Methods: In this study we utilized Nanostring immune profiling technology along with multiple in vitro and in vivo assays were used to study the role of Kaiso in breast cancer immune escape. Results: Nanostring pan cancer immune profiling demonstrated that European American breast cancer exosomes exhibited higher expression of TILs markers, T cell activation markers and CD8+T Cells markers compared to African American (p < 0.05, FDR), while we observed an increase in the expression of the anti-phagocytic molecule CD47 in breast cancer patient exosomes of African American compared to European American patients. In addition to that CD47 and SIRP-α (Signal Regulatory Protein) are highly expressed in Kaiso-scrambled MDA-MB-231 cells (sh-Scr) and exosomes, whereas THBS1, which is a regulator of CD47 expression and is regarded as angiogenesis inhibitor is significantly increased in sh-Kaiso MDA-231 cells and exosomes. Additionally, we observed that Kaiso directly binds methylated sequences in the promoter region of CD47 and THBS1 by ChIP assay. Furthermore, in vivo sh-Kaiso cells injected into athymic mice exhibited delayed tumor formation after four weeks with smaller tumor size as compared to sh-SCR cells (p < 0.05), and we observed higher expression of THBS1 with lower expression of CD47 and SIRP-α molecules by IHC and exosomes isolated from in vivo tumors (p < 0.05), indicating that Kaiso is associated with macrophage mediated immune escape. Conclusions: These findings demonstrate the important role of kaiso in immune signaling through exosomes which may be related with more aggressive cancer phenotype in breast cancer, especially in African Americans.

Characterizing the Thermodynamic Stability of the Holliday Junction Through Spectroscopic Techniques

The Holliday junction is a four‐way DNA structure formed during the process of double strand break repair and DNA recombination in meiosis. Branch migration of the junction is a vital molecular process for the transfer of genetic information from parents to offspring. Understanding this process relative to base pair composition can provide a better picture of the overall structure of the junction and its connection to short inverted repeats that have been linked to chromosome instability. We used a fluorescent nucleoside analog, 4‐amino‐6methyl‐8‐(2‐deoxy‐beta‐d‐ribofuranosyl)‐7(8H)‐pteridone (6‐MAP), to obtain site‐specific information about the melting process, through incorporation of the probe at distinct sites throughout a 34 bp immobile junction. Under our conditions, the junction primarily adopts a conformation where the arms stack co‐axially on each other. We have examined the stability of the junction arms by incorporating the probe at equivalent positions on each arm. From these measurements we have found that the junction follows a 'pseudo‐duplex' model of denaturation, in which one of the coaxially stacked pair of arms melts at a lower temperature relative to the other. Our results also point to a sequential melting pattern in which positions at the end of the arms and the center destabilize before the interior of the arms. The relative proximity to the junction center appears to be one of the factors affecting stability. Our current research investigates how sequence homology influences the stability of the junction, specifically whether the thermodynamic characteristics of an immobile junction are predictive for a mobile one. We have developed a mobile junction with 10‐bp homology in the central region. Previous research by (Voth A.R., Hays F.A., Ho P.S. (2007) Directing macromolecular conformation through halogen bonds. Proc. Natl. Acad. Sci. USA.; 104:6188–6193. doi: 10.1073/pnas.0610531104) has suggested that macromolecular conformations can be directed through the use of halogen bonds. Specific incorporation of brominated uracils in the sequence of two DNA strands of a mobile Holliday junction was shown to bias the structure to a single conformation in crystallographic experiments. Combined spectroscopic data from both the immobile and mobile junction will inform coarse‐grained modeling of the Holliday junction. Our experimental data combined with computational modeling furthers our current understanding of this DNA structure as it relates to branch migration and exchange of genetic information.

Exosomes: Dynamic Mediators of Extracellular Communication in the Tumor Microenvironment.

It is becoming increasingly recognized that the tumor microenvironment significantly contributes to the development, progression, and metastasis of cancer and also plays a role in response to treatment. The tumor microenvironment is a complex and heterogeneous niche comprised of stromal cells, cancer cells, blood vessels, areas of hypoxia and necrotic tissue, fibrosis, and extracellular matrix. Cellular communication takes place within the tumor microenvironment, both via cell to cell contact, and through extracellular mechanisms such as exosomal signaling. Exosomes are very small membrane-bound vesicles that have been shown to play key roles in the progression of cancer including modulation of the tumor microenvironment through the induction of angiogenesis, the transfer of genetic information that confers drug resistance, and increased cell migration, invasion, proliferation, and survival, as well as the modulation of immune cell interactions. The role of exosomes in several different cancers has been investigated. In the context of osteosarcoma, understanding how exosomes may modulate the tumor microenvironment to support metastatic growth particularly in the lung, the most common site of metastases, may identify novel therapeutic targets for relapsed patients.

COVID-19 and the Central Dogma: an Activity To Improve Student Learning and Engagement.

The Central Dogma of molecular biology describes the transfer of genetic information within organisms and is a core concept in the biological sciences. However foundational, the Central Dogma is often misrepresented when taught in introductory college biology courses. In particular, the Central Dogma is often taught with a requisite DNA step, an incorrect conception that omits the possibility of RNA-based molecular systems, such as SARS-CoV-2, the causative agent of COVID-19. In this new contribution, we offer a practical way to clarify correct conceptions and make them immediately relevant through COVID-19. In this new digital ‘sorting cards’ activity, students collaboratively synthesize and map their knowledge of core molecular biology. Building off of the typically-presented concepts of the Central Dogma, we also introduce two sorting card “expansion packs” for double-stranded DNA viruses and single-stranded RNA viruses. We provide activity templates for all sets of cards using a free web-based collaborative platform suitable for sudden shifts to online learning (as in our implementation), pre-planned online learning, and in-person classes. While truly hands-on activities can be difficult to replicate in the context of online learning, the use of collaborative websites and creative freedom in this activity encourages student engagement in and ownership of their learning.