Biology subjects

Tayeb-Fligelman, E.

Publications and source records attributed to Tayeb-Fligelman, E..

5 recordsLinked to original sources

bioRxiv2021

The SARS-CoV-2 nucleocapsid protein preferentially binds long and structured RNAs

The SARS-CoV-2 nucleocapsid protein (NCAP) functions in viral RNA genome packaging, virion assembly, RNA synthesis and translation, and regulation of host immune response. RNA-binding is central to these processes. Little is known how NCAP selects its binding partners in the myriad of host and viral RNAs. To address this fundamental question, we employed electrophoresis mobility shift and competition assays to compare NCAP binding to RNAs that are of SARS-CoV-2 vs. non-SARS-CoV-2, long vs. short, and structured vs. unstructured. We found that although NCAP can bind all RNAs tested, it primarily binds structured RNAs, and their association suppresses strong interaction with single-stranded RNAs. NCAP prefers long RNAs, especially those containing multiple structures separated by single-stranded linkers that presumably offer conformational flexibility. Additionally, all three major regions of NCAP bind RNA, including the low complexity domain and dimerization domain that promote formation of NCAP oligomers, amyloid fibrils and liquid-liquid phase separation. Combining these observations, we propose that NCAP-NCAP interactions that mediate higher-order structures during packaging also drive recognition of the genomic RNA and call this mechanism recognition-by-packaging. This study provides a biochemical basis for understanding the complex NCAP-RNA interactions in the viral life cycle and a broad range of similar biological processes. HIGHLIGHTSO_LINCAP primarily binds structured RNAs. C_LIO_LINCAP prefers multiple RNA structures separated by single-stranded linkers. C_LIO_LINCAP favors binding to long RNAs. C_LI

biochemistry↗

bioRxiv2021

Inhibition of amyloid formation of the Nucleoprotein of SARS-CoV-2

The SARS-CoV-2 Nucleoprotein (NCAP) functions in RNA packaging during viral replication and assembly. Computational analysis of its amino acid sequence reveals a central low-complexity domain (LCD) having sequence features akin to LCDs in other proteins known to function in liquid-liquid phase separation. Here we show that in the presence of viral RNA, NCAP, and also its LCD segment alone, form amyloid-like fibrils when undergoing liquid-liquid phase separation. Within the LCD we identified three 6-residue segments that drive amyloid fibril formation. We determined atomic structures for fibrils formed by each of the three identified segments. These structures informed our design of peptide inhibitors of NCAP fibril formation and liquid-liquid phase separation, suggesting a therapeutic route for Covid-19. One Sentence SummaryAtomic structures of amyloid-driving peptide segments from SARS-CoV-2 Nucleoprotein inform the development of Covid-19 therapeutics.

biochemistry↗

bioRxiv2020

The Amphibian Antimicrobial Peptide Uperin 3.5 is a Cross-α/Cross-β Chameleon Functional Amyloid

Antimicrobial activity is being increasingly linked to amyloid fibril formation, suggesting physiological roles for some human amyloids, which have historically been viewed as strictly pathological agents. This work reports on formation of functional cross- amyloid fibrils of the amphibian antimicrobial peptide uperin 3.5 at atomic-resolution, an architecture initially discovered in the bacterial PSM3 cytotoxin. The fibrils of uperin 3.5 and PSM3 were comprised of parallel and anti-parallel helical sheets, respectively, recapitulating properties of {beta}-sheets. Uperin 3.5 helical fibril formation was largely induced by, and formed on, bacterial cells or membrane mimetics, and led to membrane damage and cell death. Uperin 3.5 demonstrated chameleon properties, with a secondary structure switch to cross-{beta} fibrils with reduced antibacterial activity in the absence of lipids or after heat shock. These findings suggest a regulation mechanism, which includes storage of inactive peptides as well as environmentally induced activation of uperin 3.5, via chameleon cross-/{beta} amyloid fibrils.

biochemistry↗

bioRxiv2018

Structural Insights into Curli Amyloid Fibrils suggest Repurposing Anti-amyloid Compounds as Anti-biofilm Agents

Curli amyloid fibrils secreted by Enterobacteriaceae mediate host cell adhesion and contribute to biofilm formation, thereby promoting bacterial resistance to environmental stressors. Here, we present crystal structures of amyloid-forming segments from the major curlin subunit, CsgA, revealing steric zipper fibrils of tightly mated {beta}-sheets, demonstrating a structural link between curli and human pathological amyloids. We propose that these cross-{beta} segments structure the highly robust curli amyloid core. D-enantiomeric peptides, originally developed to interfere with Alzheimers disease-associated Amyloid-{beta}, inhibited CsgA fibrillation and reduced biofilm formation in Salmonella typhimurium. Moreover, CsgA fibrils cross-seeded fibrillation of Amyloid-{beta}, providing further support for the proposed structural resemblance and potential for cross-species amyloid interactions. In this study, we provide structural insights into curli formation, offer a novel strategy for disrupting amyloid-structured biofilms, and hypothesize on the formation of self-propagating prion-like species originating from a microbial source that could influence neurodegenerative diseases.\n\nSignificanceAtomic resolution structural insights into the biofilm-associated curli amyloid fibril secreted by Enterobacteriaceae revealed elements of fibrillar architecture conserved between bacterial and human amyloids. This inspired us to repurpose anti-amyloid drugs designed to target human pathological amyloids as a novel class of anti-biofilm agents. Moreover, the results provide a molecular basis for understanding interspecies cross-seeding of amyloids through the generation of prion-like agents by molecular mimicry. This raises concerns regarding human exposure to exogenous sources of amyloids, such as contaminated food and amyloid-secreting microbes. Overall, we provide a novel framework for investigating interspecies amyloid interactions at the molecular level and offer novel insights into mechanisms which may underlie the evolutionary and etiological relationships between the human and microbial amylomes.

biochemistry↗

bioRxiv2018

Toxic Determinants of Staphylococcus aureus PSMα3 Cross-α Amyloid

The phenol-soluble modulin (PSM) peptide family, secreted by Staphylococcus aureus, performs various virulence activities, some mediated by the formation of amyloid fibrils of diverse architectures. Specifically, PSM1 and PSM4 structure the S. aureus biofilm by assembling into robust cross-{beta} amyloid fibrils. PSM3, the most cytotoxic member of the family, assembles into cross- fibrils in which -helices stack into tightly mated sheets, mimicking the cross-{beta} architecture. Here we demonstrated that massive T-cell deformation and death is linked with PSM3 aggregation and co-localization with cell membranes. Our extensive mutagenesis analyses supported the role of positive charges, and especially Lys17, in interactions with the membrane, and suggested their regulation by inter- and intra-helical electrostatic interactions within the cross- fibril. We hypothesize that PSM3 cytotoxicity is governed by the ability to form cross- fibrils and involves a dynamic process of co-aggregation with cell membrane, rupturing it. HighlightsO_LIThe cytotoxic S. aureus PSM3 assembles into cross- fibrils C_LIO_LICross- fibril polymorphism and mutations-induced secondary structure switching C_LIO_LIRegulation by cross- fibril inter- and intra-helical electrostatic interactions C_LIO_LIToxicity as a putative dynamic process of PSM3 co-aggregation with membranes C_LI

biochemistry↗