ARRTI Speaker Series - 2015

June 30, 2015

Dr. George Owttrim

University of Alberta
Department of Biological Sciences
Edmonton, Alberta, Canada

"Conditional proteolysis as a regulator of gene expression: Does cold stress regulate heat stress?"

The ability of free-living microorganisms to sense and respond to abiotic changes in their environment is crucial for survival. Expression of the sole DEAD box RNA helicase, crhR, in the photosynthetic bacterium Synechocystis PCC 6803 is regulated at a minimum of three autoregulatory, CrhR-dependent and three CrhR-independent checkpoints in response to temperature stress. This implies that the rearrangement of RNA secondary structure is required for cellular response to this stress. One of the checkpoints involves the autoregulatory, CrhR-dependent conditional proteolysis of CrhR in response to temperature upshift from 20 to 30oC. A whole cell proteome time course (Richard Fahlman) has identified proteins whose abundance is altered in response to the temperature upshift in a CrhR-dependent fashion. Potentially not unexpectedly, affected proteins are associated with translation and photosynthesis. Unexpectedly, our data suggests that the cold shock protein CrhR functions in a Synechocystis heat shock response. Conditional proteolysis is a much faster way to shut down a biosynthetic pathway that traditional transcription-translation regulatory networks. In the future, we hope to utilize the conditional proteolysis system to rapidly and precisely regulate biosynthetic pathway activity for biotechnological applications.

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May 21, 2015

Dr. Martin Holcik

Apoptosis Research Centre
Children's Hospital of Eastern Ontario Research Institute
Ottawa, Ontario, Canada

"RNA Binding Proteins - It Is All About Location"

Regulation of protein expression through RNA metabolism is a key aspect of cellular homeostasis. Upon specific cellular stresses, distinct transcripts are selectively controlled to modify protein output in order to quickly, appropriately and reversibly respond to stress. This is accomplished through a large assortment of specialized RNA binding proteins (RBPs) which control diverse aspects of RNA metabolism ranging from mRNA processing to export, translation and degradation. Frequently, the same RBP can exhibit multiple roles which are dependent on its subcellular localization within the cell, suggesting that the diverse roles of RBPs in mRNA metabolism are controlled, at least in part, by the compartmentalization of these proteins. Heterogeneous nuclear ribonucleoprotein A1 (hnRNP A1) is one such RBP which normally shuttles between the nucleus and the cytoplasm, with the bulk of the protein displaying nuclear localization. During cellular stress, however, the accumulation of hnRNP A1 in the cytoplasm has different consequences for distinct mRNAs, augmenting expression of some while repressing expression of other mRNAs.

To systematically identify factors and pathways involved in hnRNP A1 localization we set out to determine the signaling molecules that regulation localization of hnNPR A1, and the biological consequences of this regulation. We screened a library of siRNA pools targeting the kinome subset of the human genome and identified several candidate kinases that regulate cytoplasmic accumulation of hnRNP A1 in response to hypertonic stress., The results of the stress and the biological consequences of interference with hnRNP A1 localization will be presented and discussed.

May 19, 2015

Dr. Elizabeth Schultz

University of Lethbridge
Department of Biological Sciences
Lethbridge, Alberta, Canada

"Vein pursuits: towards understanding the formation of plant vascular tissue"

Plant vascular tissue performs two functions critical to plant survival: transport and support. The xylem and phloem tissue provides efficient transport routes for water, minerals, photosynthates and signaling compounds. The vascular cells’ thickened walls provide structural support to the whole plant. Thus, understanding how vascular tissue is formed and patterned is critical to understanding plant water use, photosynthetic efficiency and architecture. Like many key developmental processes in plants, vascular cell fate is induced by the plant hormone auxin. Cells that will become veins transport auxin better than their neighbours, forming an auxin canal. Because of its key developmental role, the mechanism by which auxin is directed through certain cells is an area of active research. Using the model plant Arabidopsis thaliana, our research group has discovered a number of novel genes that affect auxin levels in developing vascular tissue. One group, the FORKED gene family, is unique to plants but is found in multiple copies in all vascular plants. A second gene, UNHINGED, encodes a protein whose ortholog in yeast and animals are important for vacuole trafficking. I will describe our current understanding of how these gene products act within cells to affect auxin levels through developing tissue.

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May 5, 2015

Dr. Steven Smith

Queen's University
Department of Biomedical and Molecular Sciences
Kingston, Ontario, Canada

"Molecular Basis of gene deregulation by the oncogenic transcription factor E2A-PBX1"

The E2A gene is also involved in a chromosomal translocation that results in the oncogenic transcription factor E2A-PBX1. The two activation domains of E2 (AD1 and AD2) display redundant, independent, and cooperative functions in a cell-dependent manner, at least in part through an interaction with the transcriptional co-activator CBP/p300. The AD1:CBP/p300 interaction is critical for oncogenesis. However, a molecular understanding of the E2A:CBP/p300 interaction and associated function has been lacking. Here, we describe our use of structural biology, biophysical and biochemical approaches, and complementary cell-based assays and mouse studies to characterize the interactions of AD1 of E2A with CBP/p300, and our ability to disrupt this interaction by an engineered peptide. Our studies indicate that these interactions are essential for transcriptional activation and oncogenesis and provide a structural basis for these functions.

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May 5, 2015

Dr. Alisdair Boraston

University of Victoria
Department of Biochemistry and Microbiology
Victoria, British Columbia, Canada

"From oceans to the gut: insights into seaweed biomass turnover from studies of the human gut microbiome"

Most of the photosynthetically fixed carbon present on Earth is in land plants. Photosynthetically fixed carbon in the oceans, however, is far more dynamically recycled than it is on land. Ocean plant biomass [i.e. microalgae and macroalgae (seaweed)] is estimated to be only ~1/200 that of terrestrial plant biomass yet the annual turnover rate of photosynthetically fixed carbon in the oceans is roughly equal to that on land indicating a normalized rate of recycling that is ~2-orders of magnitude greater than on land. The biochemical basis for the rapid turnover of carbon in seaweed biomass, which is primarily carbohydrate (polysaccharide) is not well understood. Such information is key to the development of complete biogeochemical models of the global carbon cycle and to unlocking abundant and farmable seaweed biomass sources as a feedstock for the generation of biofuels, the creation of high-value products, or use in other biotechnological applications.

One of the challenges in the biochemical mapping of microbial seaweed polysaccharide degrading pathways is that organisms that work in situ are typically psychrophilic, causing unique difficulties with the biochemical characterization of the enzymes making up the relevant pathways. We have turned to an unusual alternative set of microorganisms: those from the human gut microbiome. Polysaccharide degrading pathways are highly expanded in human gut bacteria and represented among these are pathways devoted to seaweed polysaccharide metabolism. The enzymes comprising the pathways from these mesophilic organisms provide a tractable alternative to the psychrophilic enzymes, allowing us to make significant inroads into the complete molecular delineation of these novel metabolic pathways. Furthermore, analysis of these pathways in gut microbes is providing unique insight into carbohydrate-driven adaptation of the gut microbiome and its individual members.

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April 8, 2015

Dr. Nora Foroud

Lethbridge Research and Development Centre
Agriculture and Agri-Food Canada
Lethbridge, Alberta, Canada

"Trichothecene Mycotoxins: Inhibitors of Eukaryotic Ribosomes and Virulence Factors in Crop Diseases"

Trichothecene mycotoxins are macrocylcic fungal metabolites known to inhibit protein synthesis in eukaryotic ribosomes. These toxins are virulence factors in Fusarium head blight disease of wheat and related cereals, and they accumulate in the kernels of Fusarium-infected cereal crops. Ingestion of trichothecene-contaminated grain can cause severe intestinal irritation in mammals, resulting in feed refusal in livestock, and can lead to a potentially fatal condition in humans and other mammals known as alimentary toxic aleukia. Trichothecenes are sesquiterpenoid compounds composed of a fused ring system (cyclohexene/tetrahydropyran/cylopentene), an epoxide function known to be essential for toxicity, and five variable R-groups. Over 200 trichothecenes have been identified and they are divided into four classes (types A-D), where the A and B types are produced by the Fusarium species involved in crop diseases, and the B type predominates. Type B trichothecenes include nivalenol, deoxynivalenol (DON) and its acetylated derivatives (3-acetyl DON and 15-acetyl DON). Different degrees of toxicity have been observed among trichothecenes, and these differences are specific to the class of organism in question. For instance, DON is known to be more phytotoxic than nivalenol, whereas the latter is more harmful in mammalian systems. While it is known that these toxins inhibit protein synthesis by disrupting peptidyl transferase activity, the exact mechanism of this inhibition is poorly understood. Furthermore, it is not known how differences in trichothecene structure can affect different levels of toxicity. Our long-term goals are to better understand the toxicity mechanisms of these compounds, and as an initial step towards this end, we have employed a series of solid-state and solution-state nuclear magnetic resonance (NMR) spectroscopy experiments to study the three-dimensional structures and hydrogen-bonding patterns of both Type A and B trichothecenes.

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March 11, 2015

Dr. Brian Dempsey

University of Western Ontario
London, Ontario, Canada
(Now at the University of Lethbridge)

"The S100 protein family: Calcium signals that control formation of protein complexes"

S100 proteins are a family of EF-hand calcium binding proteins. Most of the proteins in this family undergo a large conformational change upon calcium binding. This structural rearrangement exposes a hydrophobic protein-binding site. Calcium bound S100 proteins are then able to recruit, and bind, one or more proteins. Each S100 protein can have multiple protein binding partners and can therefore play multiple roles in the cell. S100 protein functions include regulation of protein phosphorylation, membrane repair, and cytoskeletal phosphorylation. This talk will focus on the ability of S100 proteins to form protein complexes for the regulation of cellular processes. Specifically, the regulation of dopamine signalling and p53 function by S100B as well as the ability of S100A10 to generate membrane repair complexes.

January 21, 2015

Dr. Lawrence Kawchuk

Lethbridge Research and Development Centre
Agriculture and Agri-Food Canada
Lethbridge, Alberta, Canada

"Evolution and Lifestyle of RNA Viruses"

RNA viruses frequently capture the headlines and imagination because of their acute and chronic disease capabilities. Some infamous examples of RNA viruses include Ebola, Influenza, and the Polioviruses and they share many similar characteristics. Our research with the single-stranded positive-sense Polero RNA viruses has provided insight into the complexities associated with these relatively simple pathogens. It is remarkable that given the discoveries and advances made in sequencing, cloning and gene expression, small RNA and silencing, and diagnostics that these viruses continue to cause devastating epidemics. Fortunately, advances continue to be made in our understanding of the host-pathogen interactions and innate immunity that is helping to eradicate these diseases.

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