Refereed Preprints

Review Commons provides authors with a Refereed Preprint, which includes the authors’ manuscript, reports from a single round of peer review and the authors’ response. These Refereed Preprints are transferred on the author’s behalf to bioRxiv. The most recently-completed Review Commons peer-reviews are listed below, with the most recently posted reviews at the top.

Latest Refereed Preprints

Bioinformatics | 14 Aug 2020
The chi-square periodogram (CSP), developed over 40 years ago, continues to be one of the most popular methods to estimate the period of circadian (circa 24-h) rhythms. Previous work has indicated the CSP is sometimes less accurate than other methods, but understanding of why and under what conditions remains incomplete. Using simulated rhythmic time-courses, we found that the CSP is prone to underestimating the period in a manner that depends on the true period and the length of the time-course. This underestimation bias is most severe in short time-courses (e.g., 3 days), but is also visible in longer simulated time-courses (e.g., 12 days) and in experimental time-courses of mouse wheel-running. The bias is caused by discontinuities in the periodogram that are related to the number of time-points the CSP uses to calculate the observed variance for a given test period. By revising the calculation to avoid discontinuities, we developed a new version, the greedy CSP, that shows reduced bias and improved accuracy. Nonetheless, even the greedy CSP tended to be less accurate on our simulated time-courses than an alternative method, namely the Lomb-Scargle periodogram. Thus, although our study describes a major improvement to a classic method, it also suggests that users should generally avoid the CSP when estimating the period of biological rhythms.
Immunology | 03 Sep 2020

Low immunogenicity of malaria pre-erythrocytic stages can be overcome by vaccination

Katja Müller, Matthew P. Gibbins, Arturo Reyes-Sandoval, Adrian V. S. Hill, Simon J. Draper, Kai Matuschewski, Olivier Silvie, Julius Clemence R. Hafalla

Vaccine discovery and development critically depends on predictive assays, which prioritise protective antigens. Immunogenicity is considered one important criterion for progression of candidate vaccines to further clinical evaluation, including phase I/II trials. Here, we tested this assumption in an infection and vaccination model for malaria pre-erythrocytic stages. We engineered Plasmodium berghei parasites that harbour a well-characterised epitope for stimulation of CD8+ T cells either as an antigen in the circumsporozoite protein (CSP), the surface coat protein of extracellular sporozoites or in the upregulated in sporozoites 4 (UIS4), a major protein associated with the parasitophorous vacuole membrane (PVM) that surrounds the intracellular exo-erythrocytic forms (EEF). We show that the antigen origin results in profound differences in immunogenicity with a sporozoite antigen eliciting robust and superior antigen-specific CD8+ T cell responses, whilst an EEF antigen evokes poor responses. However, despite their contrasting immunogenic properties, both sporozoite and EEF antigens gain access to antigen presentation pathways in hepatocytes, as recognition and targeting by vaccine-induced, antigen-specific effector CD8+ T cells results in high levels of protection when targeting both antigens. Our study is the first demonstration that poor immunogenicity of EEF antigens does not preclude their susceptibility to antigen-specific CD8+ T cell killing. Our findings that antigen immunogenicity is an inadequate predictor of vaccine susceptibility have wide-ranging implications on antigen prioritisation for the design and testing of next-generation pre-erythrocytic malaria vaccines.
Cell Biology | 03 Sep 2020

TRIM37 prevents formation of centriolar protein assemblies by regulating Centrobin stability

Fernando R. Balestra, Benita Wolf, Andrés Domínguez-Calvo, Alizée Buff, Tessa Averink, Marita Lipsanen-Nyman, Coralie Busso, Pablo Huertas, Rosa M. Ríos, Pierre Gönczy

TRIM37 is an E3 ubiquitin ligase mutated in Mulibrey nanism, a disease characterized by impaired growth and increased tumorigenesis, whose cellular etiology is poorly understood. TRIM37 depletion from tissue culture cells results in supernumerary foci bearing the centriolar protein Centrin. Here, we characterized these centriolar protein assemblies (Cenpas) to uncover the mechanism of action of TRIM37. We established that an atypical de novo assembly pathway is notably involved in forming Cenpas, which can nevertheless trigger further centriole assembly and act as MTOCs. We found also that Cenpas are present and act similarly in Mulibrey patient cells. Through correlative light electron microscopy, we uncovered that Cenpas correspond to centriole related structures and elongated electron-dense structures with stripes. Importantly, we established that TRIM37 regulates the stability and solubility of the centriolar protein Centrobin. Our findings suggest that elongated Centrobin assemblies are a major constituent of the striped electron dense structures. Furthermore, we established that Cenpas formation upon TRIM37 depletion requires PLK4 activity, as well as two parallel pathways relying respectively on Centrobin and PLK1. Overall, our work uncovers how TRIM37 prevents the formation of Cenpas that would otherwise threaten genome integrity, including possibly in Mulibrey patients.
Biochemistry | 15 Jun 2020

An Atlas of Phosphorylation and Proteolytic Processing Events During Excitotoxic Neuronal Death Reveals New Therapeutic Opportunities

S. Sadia Ameen, Antoine Dufour, M. Iqbal Hossain, Ashfaqul Hoque, Sharelle Sturgeon, Harshal Nandurkar, Dominik Draxler, Robert Medcalf, Mohd Aizuddin Kamaruddin, Isabelle S. Lucet, Michael G. Leeming, Dazhi Liu, Amardeep Dhillon, Jet Phey Lim, Hong-Jian Zhu, Laita Bokhari, Carli Roulston, Oded Kleifeld, D. Ciccotosto Giuseppe, Nicholas A. Williamson, Ching-Seng Ang, Heung-Chin Cheng

Excitotoxicity, a neuronal death process in neurological disorders, is initiated by over-stimulation of neuronal ionotropic glutamate receptors. The over-stimulated receptors dysregulate proteases, protein kinases and phosphatases, which in turn modify target neuronal proteins to induce cell death. To decipher this cell death mechanism, we used quantitative proteomics, phosphoproteomics and N-terminomics to identify modified proteins in excitotoxic neurons. Data, available in ProteomeXchange (identifiers: PXD019527 and PXD019211), enabled us to identify over one thousand such proteins with calpains, cathepsins and over twenty protein kinases as their major modifiers. These protein modification events can potentially perturb signalling pathways governing cell survival, synaptogenesis, axonal guidance and mRNA processing. Importantly, blocking the modification of Src protein kinase, a signalling hub in excitotoxic neurons, protected against neuronal loss in vivo in a rat model of neurotoxicity. Besides offering new insights into excitotoxic neuronal death mechanism, our findings suggest potential neuroprotective therapeutic targets for treating neurological disorders.Graphical abstractMulti-dimensional proteomic analysis identified proteins modified by proteolysis and altered phosphorylation in neurons undergoing excitotoxic cell death.Calpains, cathepsins and over twenty protein kinases are major modifiers of these proteins.These protein modification events are predicted to impact cell survival, axonal guidance, synaptogenesis and mRNA processing.Blocking modification of an identified protein Src, which acts as a major signalling hub in neurons, was protective against excitotoxic injury in vivo.In BriefUsing multidimensional proteomic approaches, Ameen, et al. mapped the changes of proteome, phosphoproteome and N-terminome of cultured primary neurons during excitotoxicity, a crucial neuronal death process in neurological disorders. These proteomic changes document new excitotoxicity-associated molecular events, and offer insights into how these events are organized to induce neuronal death. Potential therapeutic relevance of these molecular events is illustrated by the demonstration that in vivo blockade of one of these events could protect against excitotoxic neuronal loss.
Molecular Biology | 06 Jul 2020

Expanded CAG/CTG Repeats Resist Gene Silencing Mediated by Targeted Epigenome Editing

Bin Yang, Alicia C. Borgeaud, Lorène Aeschbach, Oscar Rodríguez-Lima, Gustavo A. Ruiz Buendía, Cinzia Cinesi, Tuncay Baubec, Vincent Dion

Expanded CAG/CTG repeat disorders affect over 1 in 2500 individuals worldwide. Potential therapeutic avenues include gene silencing and modulation of repeat instability. However, there are major mechanistic gaps in our understanding of these processes that prevent the rational design of an efficient treatment. To address this, we developed a novel system, ParB/ANCHOR-mediated Inducible Targeting (PInT), in which any protein can be recruited at will to a GFP reporter containing an expanded CAG/CTG repeat. Using PInT, we determined that neither the histone deacetylase HDAC5 nor the DNA methyltransferase DNMT1 modulate repeat instability upon targeting to the expanded repeat, suggesting that their effect is independent of local chromatin structure. Unexpectedly, we found that expanded CAG/CTG repeats reduce the effectiveness of gene silencing mediated by HDAC5 or DNMT1 targeting. The repeat-length effect in gene silencing by HDAC5 was abolished by a small molecule inhibitor of HDAC3. Our results have important implications on the design of epigenome editing approaches for expanded CAG/CTG repeat disorders. PInT is a versatile synthetic system to study the effect of any sequence of interest on epigenome editing.
Evolutionary Biology | 14 Sep 2020
Across the Tree of Life (ToL), the complexity of proteomes varies widely. Our systematic analysis depicts that from the simplest archaea to mammals, the total number of proteins per proteome expanded ~200-fold. Individual proteins also became larger, and multi-domain proteins expanded ~50-fold. Apart from duplication and divergence of existing proteins, completely new proteins were born. Along the ToL, the number of different folds expanded ~5-fold and fold-combinations ~20-fold. Proteins prone to misfolding and aggregation, such as repeat and beta-rich proteins, proliferated ~600-fold, and accordingly, proteins predicted as aggregation-prone became 6-fold more frequent in mammalian compared to bacterial proteomes. To control the quality of these expanding proteomes, core-chaperones, ranging from HSP20s that prevent aggregation to HSP60, HSP70, HSP90, and HSP100 acting as ATP-fueled unfolding and refolding machines, also evolved. However, these core-chaperones were already available in prokaryotes, and they comprise ~0.3% of all genes from archaea to mammals. This challenge—roughly the same number of core-chaperones supporting a massive expansion of proteomes, was met by (i) higher cellular abundances of the ancient generalist core-chaperones, and (ii) continuous emergence of new substrate-binding and nucleotide-exchange factor co-chaperones that function cooperatively with core-chaperones, as a network.
Biochemistry | 03 Sep 2020

Peroxisomes contribute to intracellular calcium dynamics

Yelena Sargsyan, Uta Bickmeyer, Katrin Streckfuss-Bömeke, Ivan Bogeski, Sven Thoms

Peroxisomes communicate with other cellular compartments by transfer of various metabolites. However, whether peroxisomes are sites for calcium handling and exchange has remained contentious. Here we generated sensors for assessment of peroxisomal calcium and applied them for single cell-based calcium imaging in HeLa cells and cardiomyocytes. We found that peroxisomes in HeLa cells take up calcium upon depletion of intracellular calcium stores and upon calcium influx across the plasma membrane. Further, we show that peroxisomes of neonatal rat cardiomyocytes and human induced pluripotent stem cell-derived cardiomyocytes can take up calcium in a controlled manner. Our results indicate that peroxisomal and cytosolic calcium signals are tightly interconnected. Hence, peroxisomes may play an important role in shaping cellular calcium dynamics by serving as buffers or sources of intracellular calcium.
Cell Biology | 15 May 2020

CRYPTOCHROMES confer robustness, not rhythmicity, to circadian timekeeping

Marrit Putker, David Wong, Estere Seinkmane, Nina Marie Rzechorzek, Aiwei Zeng, Nathaniel P. Hoyle, Johanna E. Chesham, Mathew D. Edwards, Kevin A. Feeney, Robin Fischer, Nicolai Peschel, Ko-Fan Chen, Christopher P. Selby, Aziz Sancar, John S. O’Neill

Circadian (approximately daily) rhythms are a pervasive property of mammalian cells, tissues, and behaviour, ensuring physiological and metabolic adaptation to solar time. Models of daily cellular timekeeping revolve around transcriptional feedback repression, whereby CLOCK and BMAL1 activate the expression of ‘clock proteins’ PERIOD (PER) and CRYPTOCHROME (CRY), which in turn repress CLOCK/BMAL1 activity. CRY proteins are thus considered essential negative regulators of the oscillation; a function supported by behavioural arrhythmicity of CRY-deficient mice when kept under constant conditions. Challenging this interpretation, however, we find evidence for persistent circadian rhythms in mouse behaviour and cellular PER2 levels when CRY is absent. CRY-less oscillations are variable in their expression and have a shorter period than wild type controls. Importantly, we find classic circadian hallmarks such as temperature compensation and determination of period by casein kinase 1δ/ε activity to be maintained. In the absence of CRY-mediated transcriptional feedback repression and rhythmic Per2 transcription, PER2 protein rhythms are sustained for several cycles, accompanied by circadian variation in protein stability. We suggest that, whereas circadian transcriptional feedback imparts robustness and functionality onto biological clocks, the core timekeeping mechanism is post-translational. Our findings suggest that PER proteins normally act as signalling hubs that transduce timing information to the nucleus, imparting daily rhythms upon the activity of transcriptional effectors.➢PER/CRY-mediated negative feedback is dispensable for mammalian circadian timekeeping➢Circadian variation in PER2 levels persists in the absence of rhythmic Per2 transcription➢CK1 and GSK3 are plausible mechanistic components of a ‘cytoscillator’ mechanism➢CRY-mediated feedback repression imparts robustness to biological timekeepingIn briefCircadian turnover of mammalian clock protein PERIOD2 persists in the absence of canonical transcriptional feedback repression and rhythmic clock gene activity, demanding a re-evaluation of cellular clock function and evolution.
Neuroscience | 27 Jun 2020

Prions induce minor genome-wide translational changes in neurons compared to glia

Claudia Scheckel, Marigona Imeri, Petra Schwarz, Adriano Aguzzi

Prion diseases are caused by PrPSc, a self-replicating pathologically misfolded protein that exerts toxicity predominantly in the brain. The administration of PrPSc causes a robust, reproducible and specific disease manifestation. Here we have applied a combination of translating ribosome affinity purification and ribosome profiling to identify biologically relevant prion-induced changes during disease progression in a cell-type specific and genome-wide manner. Terminally diseased mice with severe neurological symptoms showed extensive alterations in astrocytes and microglia. Surprisingly, we detected only minor changes in the translational profiles of neurons. Prion-induced alterations in glia overlapped with those identified in other neurodegenerative diseases, suggesting that similar events occur in a broad spectrum of pathologies. Our results suggest that aberrant translation within glia may suffice to cause severe neurological symptoms and may even be the primary driver of prion disease.
Cell Biology | 30 Jun 2020

Heh2/Man1 may be an evolutionarily conserved sensor of NPC assembly state

Sapan Borah, David J. Thaller, Zhanna Hakhverdyan, Elisa C. Rodriguez, Michael P. Rout, Megan C. King, C. Patrick Lusk

Integral membrane proteins of the Lap2-emerin-MAN1 (LEM) family have emerged as important components of the inner nuclear membrane (INM) required for the functional and physical integrity of the nuclear envelope. However, like many INM proteins, there is limited understanding of the biochemical interaction networks that enable LEM protein function. Here, we show that Heh2/Man1 can be affinity purified with major scaffold components of the nuclear pore complex (NPC), specifically the inner ring complex, in evolutionarily distant yeasts. Interactions between Heh2 and nucleoporins is mediated by its C-terminal winged-helix (WH) domain and are distinct from interactions required for INM targeting. Disrupting interactions between Heh2 and the NPC leads to NPC clustering. Interestingly, Heh2’s association with NPCs can also be broken by knocking out Nup133, a component of the outer ring that does not physically interact with Heh2. Thus, Heh2’s association with NPCs depends on the structural integrity of both major NPC scaffold complexes. We propose a model in which Heh2 acts as a sensor of NPC assembly state, which may be important for NPC quality control mechanisms and the segregation of NPCs during cell division.
Molecular Biology | 02 Sep 2020

A stress-induced Tyrosine tRNA depletion response mediates codon-based translational repression and growth suppression

Doowon Huh, Maria C. Passarelli, Jenny Gao, Shahnoza N Dusmatova, Clara Goin, Lisa Fish, Alexandra M. Pinzaru, Henrik Molina, Elizabeth A. McMillan, Hosseinali Asgharian, Hani Goodarzi, Sohail F. Tavazoie

Eukaryotic transfer RNAs can become selectively fragmented upon various stresses, generating tRNA-derived small RNA fragments. Such fragmentation has been reported to impact a small fraction of the tRNA pool and thus presumed to not directly impact translation. We report that oxidative stress can rapidly generate tyrosine tRNAGUA fragments in human cells—causing significant depletion of the precursor tRNA. Tyrosine tRNAGUA depletion impaired translation of growth and metabolic genes enriched in cognate tyrosine codons. Depletion of tyrosine tRNAGUA or its translationally regulated targets USP3 and SCD repressed proliferation—revealing a dedicated tRNA-regulated growth suppressive pathway for oxidative stress response. Tyrosine fragments are generated in a DIS3L2 exoribonuclease-dependent manner and inhibit hnRNPA1-mediated transcript destabilization. Moreover, tyrosine fragmentation is conserved in C. elegans. Thus, tRNA fragmentation can coordinately generate trans-acting small-RNAs and functionally deplete a tRNA. Our findings reveal the existence of an underlying adaptive codon-based regulatory response inherent to the genetic code.
Cell Biology | 01 Jul 2020

High-content Imaging-based Pooled CRISPR Screens in Mammalian Cells

Xiaowei Yan, Nico Stuurman, Susana A. Ribeiro, Marvin E. Tanenbaum, Max A. Horlbeck, Christina R. Liem, Marco Jost, Jonathan S. Weissman, Ronald D. Vale

CRISPR (clustered regularly interspaced short palindromic repeats) -based gene inactivation provides a powerful means of linking genes to particular cellular phenotypes. CRISPR-based screening has mostly relied upon using large genomic pools of single guide RNAs (sgRNAs). However, this approach is limited to phenotypes that can be enriched by chemical selection or FACS sorting. Here, we developed a microscopy-based approach, which we name optical enrichment, to computationally select cells displaying a particular CRISPR-induced phenotype, mark them by photo-conversion of an expressed photo-activatable fluorescent protein, and then isolate the fluorescent cells using fluorescence-activated cell sorting (FACS). A plugin was developed for the open source software μManager to automate the phenotypic identification and photo-conversion of cells, allowing ~1.5 million individual cells to be screened in 8 hr. We used this approach to screen 6092 sgRNAs targeting 544 genes for their effects on nuclear size regulation and identified 14 bona fide hits. These results present a highly scalable approach to facilitate imaging-based pooled CRISPR screens.
Bioinformatics | 16 Jun 2020

Mapping the Algal Secret Genome: The small RNA Locus Map for Chlamydomonas reinhardtii

Sebastian Y. Müller, Nicholas E. Matthews, Adrian A. Valli, David C. Baulcombe

Small (s)RNAs play crucial roles in the regulation of gene expression and genome stability across eukaryotes where they direct epigenetic modifications, post-transcriptional gene silencing, and defense against both endogenous and exogenous viruses. The green alga Chlamydomonas reinhardtii is a well-studied unicellular alga species with sRNA-based mechanisms that are distinct from those of land plants. It is, therefore, a good model to study sRNA evolution but a systematic classification of sRNA mechanisms is lacking in this and any other algae. Here, using data-driven machine learning approaches including Multiple Correspondence Analysis (MCA) and clustering, we have generated a comprehensively annotated and classified sRNA locus map for C. reinhardtii. This map shows some common characteristics with higher plants and animals, but it also reveals distinct features. These results are consistent with the idea that there was diversification in sRNA mechanisms after the evolutionary divergence of algae from higher plant lineages.
Systems Biology | 22 May 2020

A large accessory protein interactome is rewired across environments

Zhimin Liu, Darach Miller, Fangfei Li, Xianan Liu, Sasha Levy

To characterize how protein-protein interaction (PPI) networks change, we quantified the relative PPI abundance of 1.6 million protein pairs in yeast across 9 growth conditions, with replication, for a total of 44 million measurements. Our multi-condition screen identified 13,764 pairwise PPIs, a 3-fold increase over PPIs identified in one condition. A few “immutable” PPIs are present across all conditions, while most “mutable” PPIs are rarely observed. Immutable PPIs aggregate into highly connected “core” network modules, with most network remodeling occurring within a loosely connected “accessory” module. Mutable PPIs are less likely to co-express, co-localize, and be explained by simple mass action kinetics, and more likely to contain proteins with intrinsically disordered regions, implying that environment-dependent association and binding is critical to cellular adaptation. Our results show that protein interactomes are larger than previously thought and contain highly dynamic regions that reorganize to drive or respond to cellular changes.
Developmental Biology | 28 May 2020

C. elegans establishes germline versus soma by balancing inherited histone methylation

Brandon S. Carpenter, Teresa W. Lee, Caroline F. Plott, Jovan S. Brockett, Dexter A. Myrick, David J. Katz

Embryos undergo extensive reprogramming at fertilization to prevent the inappropriate inheritance of histone methylation. In C. elegans, this reprogramming is mediated by the H3K4me2 demethylase, SPR-5, and the H3K9 methyltransferase, MET-2. In contrast to this reprogramming, the H3K36 methyltransferase, MES-4, maintains H3K36me2/3 at germline genes between generations to help re-establish the germline. To determine whether the MES-4 germline inheritance system antagonizes spr-5; met-2 reprogramming, we examined the interaction between these two systems. We find that the developmental delay of spr-5; met-2 mutant progeny is associated with ectopic H3K36me2/3 and the ectopic expression of MES-4 targeted germline genes in somatic tissues. Furthermore, the developmental delay is dependent upon MES-4 and the H3K4 methyltransferase, SET-2. We propose that the MES-4 inheritance system prevents critical germline genes from being repressed by maternal spr-5; met-2 reprogramming. Thus, the balance of inherited histone modifications is necessary to distinguish germline versus soma and prevent developmental delay.
Biophysics | 03 Jun 2020

Implications for tetraspanin-enriched microdomain assembly based on structures of CD9 with EWI-F

Wout Oosterheert, Katerina T. Xenaki, Viviana Neviani, Wouter Pos, Sofia Doulkeridou, Jip Manshande, Nicholas M. Pearce, Loes M. J. Kroon-Batenburg, Martin Lutz, Paul M. P. van Bergen en Henegouwen, Piet Gros

Tetraspanins are ubiquitous eukaryotic membrane proteins that contribute to a variety of signaling processes by spatially organizing partner-receptor molecules in the plasma membrane. How tetraspanins bind and cluster partner receptors into so-called tetraspanin-enriched microdomains is unknown. Here we present crystal structures of the large extracellular loop of CD9 in complex with nanobodies 4C8 and 4E8; and, the cryo-EM structure of 4C8-bound CD9 in complex with its prototypical partner EWI-F. The CD9 - EWI-F complex displays a tetrameric arrangement with two centrally positioned EWI-F molecules, dimerized through their ectodomains, and two CD9 molecules, one bound to each EWI-F single-pass transmembrane helix through CD9-helices h3 and h4. In the crystal structures, nanobodies 4C8 and 4E8 bind CD9 at the C and D loop, in agreement with 4C8 binding at the ends of the CD9 - EWI-F cryo-EM complex. Overall, the 4C8 - CD9 - EWI-F - EWI-F - CD9 - 4C8 complexes varied from nearly two-fold symmetric (i.e. with the two CD9 - 4C8 copies in nearly anti-parallel orientation) to ca. 50° bent arrangements. Since membrane helices h1 and h2 and the EC2 D-loop have been previously identified as sites for tetraspanin homo-dimerization, the observed linear but flexible arrangement of CD9 - EWI-F with potential CD9 - CD9 homo-dimerization at either end provides a new ‘concatenation model’ for forming short linear or circular assemblies, which may explain the occurrence of tetraspanin-enriched microdomains.
Microbiology | 31 Jul 2020

Ebola and Marburg virus infection in bats induces a systemic response

Anitha D. Jayaprakash, Adam J. Ronk, Abhishek N. Prasad, Michael F. Covington, Kathryn R. Stein, Toni M. Schwarz, Saboor Hekmaty, Karla A. Fenton, Thomas W Geisbert, Christopher F. Basler, Alexander Bukreyev, Ravi Sachidanandam

The filoviruses Ebola (EBOV) and Marburg (MARV) cause fatal disease in humans and nonhuman primates but are associated with subclinical infections in bats, with Egyptian rousette bat (ERB, Rousettus aegyptiacus) being a natural MARV reservoir. To understand the nature of this resistance, we have analyzed how EBOV and MARV affect the transcriptomes of multiple ERB tissues. We have found that while the primary locus of infection was the liver, gene expression was affected in multiple tissues, suggesting a systemic response. We have identified transcriptional changes that are indicative of inhibition of the complement system, induction of vasodilation, changes in coagulation, modulation of iron regulation, activation of a T cell response, and converting macrophages from the M1 to M2 state. We propose that these events are facets of a systemic anti-inflammatory state that enables effective control of the infection in bats and suggest that dissecting this state can inform how to control a filovirus infection in humans.
Genomics | 21 Jul 2020

Increased processing of SINE B2 non coding RNAs unveils a novel type of transcriptome de-regulation underlying amyloid beta neuro-pathology

Yubo Cheng, Babita Gollen, Luke Saville, Christopher Isaac, Jogender Mehla, Majid Mohajerani, Athanasios Zovoilis

More than 97% of the mammalian genome is non-protein coding, and repetitive elements account for more than 50% of noncoding space. However, the functional importance of many non-coding RNAs generated by these elements and their connection with pathologic processes remains elusive. We have previously shown that B2 RNAs, a class of non-coding RNAs that belong to the B2 family of SINE repeats, mediate the transcriptional activation of stress response genes (SRGs) upon application of a stimulus. Notably, B2 RNAs bind RNA Polymerase II (RNA Pol II) and suppress SRG transcription during pro-stimulation state. Upon application of a stimulus, B2 RNAs are processed into fragments and degraded, which in turn releases RNA Pol II from suppression and upregulates SRGs. Here, we demonstrate a novel role for B2 RNAs in transcriptome response to amyloid beta toxicity and pathology in the mouse hippocampus. In healthy hippocampi, activation of SRGs is followed by a transient upregulation of pro-apoptotic factors, such as p53 and miRNA-34c, which target SRGs creating a negative feedback loop that facilitates transition to the pro-stimulation state. Using an integrative RNA genomics approach, we show that in mouse hippocampi of an amyloid precursor protein knock-in mouse model and in an in vitro cell culture model of amyloid beta toxicity, this regulatory loop is dysfunctional due to increased levels of B2 RNA processing, constitutively elevated SRG expression and high p53 levels. Evidence indicates that Hsf1, a master regulator of stress response, mediates B2 RNA processing in cells, and is upregulated during amyloid toxicity accelerating the processing of SINE RNAs and SRG hyper-activation. Our study reveals that in mouse, SINE RNAs constitute a novel pathway deregulated in amyloid beta pathology, with potential implications for similar cases in the human brain, such as Alzheimer’s disease (AD). This data attributes a role to SINE RNA processing in a pathological process as well as a new function to Hsf1 that is independent of its transcription factor activity.