Genomes are routinely subjected to DNA damage. But most cells have DNA repair systems that enforce genome stability and, ideally, prevent diseases like cancer. The trouble gets serious when these systems break down. When that happens, damage such as unrepaired DNA lesions can lead to tumors, and genomic chaos ensues.
“Double-strand breaks are one of the most dangerous types of DNA damage a cell can experience,” said Chance Meers, a postdoctoral researcher at Columbia University who earned his Ph.D. in molecular genetics in 2019 in the lab of Francesca Storici at the Georgia Institute of Technology. “They inhibit the cell’s ability to replicate its DNA, stalling cell division until the damage is repaired.”
The most accurate pathway of DNA-break repair is by using a homologous DNA sequence to template the re-synthesis of the damaged DNA region. Researchers in the Storici lab previously showed that a homologous RNA sequence could also mediate this break repair, and sought to understand the molecular mechanisms that control this process. They wrote about it in a recently published paper for the journal Molecular Cell.
“This is really about RNA’s capacity to transfer information to DNA that could be used in repairing damage,” explained Storici, professor in the School of Biological Sciences and a researcher in the Petit Institute for Bioengineering and Bioscience at Georgia Tech.
In a 2014 article published in Nature, her team explained how transcript-RNA could serve as a template for the repair of a DNA double-strand break. In this new study, according to lead author Meers, “we found that not only can RNA serve as a template for the repair of double-strand breaks, but that it was modifying genomic information in the absence of double-strand breaks.”
This modification of DNA even in the absence of an induced double-strand break was very surprising to the team. Also unanticipated, said Meers, was that the process of transferring information depended on the presence of an unexpected enzyme, DNA polymerase Zeta.
“This is quite surprising, because DNA polymerase Zeta is part of a large class of enzymes known as DNA polymerases characterized by their ability to catalyze the synthesis of DNA molecules from a DNA template,” Meers said.
Polymerase Zeta is part of a subset of DNA polymerases known as translesion DNA polymerases, which have unique properties that allow them to synthesize damaged DNA caused by mutagens like UV radiation. Translesion DNA polymerases also are important in cellular processes like the diversification of B-cell receptors used to recognize foreign elements like viruses.
Meers explained that RNA molecules can be thought of as the cache on a computer – or a short-term memory that is not stably maintained.
“We use a novel assay in which the yeast chromosomal DNA was genetically engineered to contain a piece of DNA sequence that allows it to be removed only in the RNA that is actively transcribed from the chromosomal DNA, generating a change in the RNA sequence but not in the DNA,” he said.
If this “short-term memory,” in the form of RNA, is transferred back into the DNA sequence during the process of RNA-templated DNA repair, it becomes “long-term memory” stored in the DNA, which can be thought of as the hard drive.
“We placed this system into a particular gene in yeast, which gives an observable characteristic trait if this process occurred, allowing us to track the repair process,” Meers said.
Exploiting such an assay, along with the discovery of a new role for DNA polymerase Zeta in RNA-templated DNA repair and modification, the study contains a series of new findings that helped the team better understand the genetic and molecular mechanisms by which RNA can change DNA sequences in cells.
This research essentially lays the groundwork for exploring the role that RNA can play in modifying genomic sequence and should allow future studies to more directly explore the role of RNA in genomic instability and, in particular, in other organisms, like humans.
This work was supported by the National Cancer Institute (NCI) and the National Institute of General Medical Sciences (NIGMS) of the NIH (grant numbers CA188347, P30CA056036 and GM136717 to A.V.M.), Drexel Coulter Program Award (to A.V.M.), the National Institute of General Medical Sciences (NIGMS) of the NIH (grant number GM115927 to F.S.), the National Science Foundation fund (grant number 1615335 to F.S.), the Howard Hughes Medical Institute Faculty Scholar (grant number 55108574 to F.S.), and grants from the Southeast Center for Mathematics and Biology (NSF, DMS-1764406 and Simons Foundation, 594594 to F.S.). Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the NSF.
CITATION: Chance Meers, Havva Keskin, Gabor Banyai, Olga Mazina, Taehwan Yang, Alli L. Gombolay, Kuntal Mukherjee, Efiyenia I. Kaparos, Gary Newnam, Alexander Mazin, and Francesca Storici. “Genetic characterization of three distinct mechanisms supporting RNA-driven DNA repair and 3 modification reveals major role of DNA polymerase Zeta.” (Molecular Cell, 2020) (https://www.cell.com/molecular-cell/fulltext/S1097-2765(20)30554-2
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The Suddath Symposium, presented in a virtual format this year, is held annually to celebrate the life and contribution of F.L. "Bud" Suddath by discussing the latest developments in the fields of bioengineering and bioscience. The speakers include leading researchers across the world. This successful symposium has been taking place for 29 years! Each year the symposium topic changes.
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The 2021 Suddath Symposium is supported by the Parker H. Petit Institute of Bioengineering and Bioscience at Georgia Tech.
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This virtual talk is a follow-up to Campus Surveillance Testing Town Halls held August 4 and August 20.
Patton Distinguished Professors Joshua S. Weitz and Greg Gibson will join JulieAnne Williamson, Executive Director of Sustainability and Building Operations at Georgia Tech and Team Lead for Campus Surveillance Testing Operations, to discuss campus cases and tracking, actions taken to date, and next steps.
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Saad Bhamla, Ph.D.
Chemical and Biomolecular Engineering
Georgia Instutute of Technology
ABSTRACT
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Host: David Hu, Ph.D.
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Daniel Richter, Ph.D.
Institut de Biologia Evolutiva
ABSTRACT
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Host: Alberto Stolfi, Ph.D.
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Nicole Hellessey, Ph.D.
School of Biological Sciences
Georgia Institute of Technology
ABSTRACT
Antarctic krill (Euphausia superba) is a key component of the Antarctic food web with considerable lipid reserves that are vital for both their own and higher predator survival. Krill feed on diatoms, dinoflagellates and other algal species year-round, resulting in high omega-3 polyunsaturated fatty acids which are essential for krill health, growth and reproduction. Krill-derived omega-3 containing products (particularly eicosapentacnoic acid (20:5w3) and docosahexaenoic acid (22:6w3)) are sold as nutraceuticals for human consumption. Krill oil tablets (sold as an omega-3 supplement) are now one of the fastest growing nutraceuticals globally. However, few attempts have been made to link the spatial and temporal variations in krill lipids to those in their food supply. Knowledge of krill diet and krill lipid dynamics is lacking for the Indian and Pacific Oceans, as most studies have focused on the South Atlantic Ocean sector where the krill fishery is based. Most research voyages are conducted during the summer and all scientific studies are restricted in their spatial and temporal scales. Another major gap in current Antarctic ecosystem models is the link between environmental drivers and their impact on primary production and therefore food availability. Satellite-derived data for biological and ecological measures is still developing as a tool although outputs such as ocean colour data which can be converted into chlorophyll a concentrations (a proxy for primary production), are becoming more common. This seminar will cover recent developments in the knowledge of spatiotemporal fluctuations of krill lipid biochemistry in relation to their environment.
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Kai Ziervogel, Ph.D.
Institute for the Study of Earth, Oceans and Space
University of New Hampshire
ABSTRACT
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Audrey Sederberg, Ph.D.
Department of Physics
Emory University
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A central goal of neuroscience is to connect structure to function: to understand how neural activity and neuroanatomy control the actions, perception, and cognition of an organism. In recent years, there has been an explosion in the quantity and quality of neural data. Only ten years ago, recording simultaneously from a few dozen cells was notable, and now that number is in the thousands. We also know more about the intricacies of microcircuit anatomy, with detailed information on individual cell types and the patterns of connectivity among them. These data are exciting, but also raise challenging questions and require integrating precise, quantitative predictions into the analysis of large, complex datasets. In my talk, I will focus on two examples of how new directions in theoretical and data-analytic research can lead to novel insight into the function of neural circuits. First, I will show how minimally structured networks can capture many features of large-scale neural population recordings with surprising precision (within a few percent!), suggesting new approaches for linking structure to function. In the second part of the talk, I will show how we use prediction to extract essential features of a dynamic cortical state, a general approach that can be extended across brain areas and species to build a quantitative, comparative framework for the analysis of cortical dynamics. These are steps toward the ultimate goal of predicting, from the anatomy of a microcircuit, both the statistics of activity (e.g., selectivity, correlations, power spectra) that it generates and how that activity supports microcircuit computations relevant to behavior.
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Joseph Lachance, Ph.D.
School of Biological Sciences
Georgia Institute of Technology
ABSTRACT
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