Biology subjects

Shenfeld, A.

Publications and source records attributed to Shenfeld, A..

3 recordsLinked to original sources

bioRxiv2026

OLD sentinel: an abortive tRNase surveys phage replication and DNA defects in RecBCD-compromised cells

OLD, an abortive immunity protein from prophage P2, consists of an ABC ATPase sensor and a TOPRIM nuclease effector -- a core architecture shared by a large protein family, including components of antiphage systems Gabija, PARIS, Septu, and Lamassu. OLD was originally identified for its lethality in recB-deficient cells and inhibition of bacteriophage {lambda} infection, but the mechanisms governing its activation have remained elusive. Here, we present the cryo-EM structure of an inactive OLD tetramer and show that destabilization into dimeric form opens the TOPRIM catalytic site, stimulating tRNA cleavage. This activity arrests translation, a phenotype rescued by phage-encoded tRNAs. We demonstrate that OLD activation is not strictly RecBCD-dependent: OLD binds aberrant DNA structures in recB-deficient cells, but activation during infection requires recognition of single-stranded DNA hairpins at the phage replication origin. Collectively, our findings reveal how host and phage DNA processing factors create a complex landscape controlling OLD-mediated immunity.

molecular biology↗

bioRxiv2026

Phages infecting the common gut commensal Escherichia coli HS reveal tropism for its Klebsiella-like capsule

Tailed dsDNA phages are ubiquitous and thought to infect almost any bacterial species. Escherichia coli HS - a commensal strain used as a model in gut colonization studies - has not been reported as a host for dsDNA phages and is resistant to more than 100 coliphages from the BASEL collection. Here, we report the first phages infecting E. coli HS, characterize their interaction with an endogenous BREX system, and provide a detailed genomic and phylogenetic description. Phages {phi}HS1 (Queuovirinae) and {phi}HS2 (Ackermannviridae) possess dPreQ and 5-NeOmdU modifications that confer resistance to restriction digestion. {phi}HS3 is a temperate phage, related to the native HS prophage {phi}HS4, and represents a founding member of a novel genus (Hueyvirus) of P22-like phages capable of lateral transduction. We reveal exchange of tailspike genes between {phi}HS2, {phi}HS3, and Klebsiella-specific phages. Furthermore, we demonstrate that E. coli HS encodes a Klebsiella-like K47 capsule required for phage infection. These results suggest that the broad phage resistance of E. coli HS may be linked to its capsular type.

microbiology↗

bioRxiv2019

Amyloid conformers of the FXR1 protein prevent mRNA degradation in cortical neurons

Functional amyloids regulate vital processes in a variety of organisms from bacteria to higher eukaryotes. The development of methods enabling large-scale screening for amyloids opens up opportunity for systemic analysis of the prevalence of amyloids in nature. Using an original proteomic approach, we identified several proteins forming amyloid-like detergent-resistant aggregates in the rat brain. One of them is the FXR1 protein, which is known to regulate memory and emotions (1, 2). We demonstrated that in brain FXR1 forms amyloid oligomers and insoluble detergent-resistant aggregates that strongly colocalize with amyloid-specific dye Thioflavin S and bind mRNA molecules. Moreover, we demonstrated that mRNAs colocalized with FXR1 amyloid particles are completely resistant to treatment with RNAse A. Taking into consideration that the members of ribonuclease A superfamily function in neurons (3) we can conclude that amyloid conformers of FXR1 control RNA stability in brain. Thus, in contrast to pathological amyloids that cause neurodegeneration, FXR1 is the functional amyloid in forebrain. We showed that amyloid properties of FXR1 depend on its N-terminal part from 1 to 379 amino acids. This fragment forms amyloid fibrils in vitro that bind Congo red and manifest apple-green birefringence when assayed by polarization microscopy. The amyloid-forming region of FXR1 is highly conserved in mammals. These data suggest that the ability of amyloid conformers of FXR1 to protect mRNAs is characteristic of different mammalian species, including humans. Significance StatementAmyloids are highly ordered cross-{beta} sheet protein fibrils associated with many neurodegenerative diseases including Alzheimers disease. However, some amyloid proteins regulate vital processes. We identified a set of proteins that form amyloid-like aggregates in the brain of healthy rats. One of them - the FXR1 protein is known to regulate memory and emotions. FXR1 forms amyloid fibrils that bind RNA molecules and prevent their degradation in brain cortex neurons. Amyloid-forming sequence of FXR1 is highly conserved across mammals including human. Discovery of functional amyloids in mammalian brain shows that strategy aimed at the development of universal anti-amyloid drugs is unpromising. Such potential drugs should prevent or suppress formation of pathological aggregates of a certain protein, but not affect functional amyloids.

neuroscience↗