A194 IMPACT OF SUPPRESSOR OF CYTOKINE SIGNALING 1 (SOCS1) EXPRESSION IN INTESTINAL EPITHELIAL CELLS ON THE GUT MICROBIOTA

NOT PUBLISHED AT AUTHOR’S REQUEST

Disclosure of Interest

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A bacteriophage nucleus-like compartment shields DNA from CRISPR nucleases

All viruses require strategies to inhibit or evade the immunity pathways of cells they infect. The viruses that infect bacteria, bacteriophages (phages), must avoid nucleic-acid targeting immune pathways such as CRISPR-Cas (clustered regularly interspaced short palindromic repeats and CRISPR-associated genes) and restriction-modification (R-M) systems to replicate efficiently¹. Here, we show that jumbo phage ΦKZ, infecting Pseudomonas aeruginosa, segregates its DNA from immunity nucleases by constructing a proteinaceous nucleus-like compartment. ΦKZ resists many DNA-targeting immune systems in vivo, including two CRISPR-Cas3 subtypes, Cas9, Cas12a, and the restriction enzymes HsdRMS and EcoRI. Cas and restriction enzymes are unable to access the phage DNA throughout the infection, but engineered re-localization of EcoRI inside the compartment enables phage targeting and cell protection. Moreover, ΦKZ is sensitive to the RNA targeting CRISPR-Cas enzyme, Cas13a, likely due to phage mRNA localizing to the cytoplasm. Collectively, we propose that Pseudomonas jumbo phages evade a broad spectrum of DNA-targeting nucleases through the assembly of a protein barrier around their genome.

Discovery of widespread type I and type V CRISPR-Cas inhibitors

Bacterial CRISPR-Cas systems protect their host from bacteriophages and other mobile genetic elements. Mobile elements, in turn, encode various anti-CRISPR (Acr) proteins to inhibit the immune function of CRISPR-Cas. To date, Acr proteins have been discovered for type I (subtypes I-D, I-E, and I-F) and type II (II-A and II-C) but not other CRISPR systems. Here, we report the discovery of 12 acr genes, including inhibitors of type V-A and I-C CRISPR systems. AcrVA1 inhibits a broad spectrum of Cas12a (Cpf1) orthologs-including MbCas12a, Mb3Cas12a, AsCas12a, and LbCas12a-when assayed in human cells. The acr genes reported here provide useful biotechnological tools and mark the discovery of acr loci in many bacteria and phages.

How bacteria control the CRISPR-Cas arsenal

CRISPR-Cas systems are adaptive immune systems that protect their hosts from predation by bacteriophages (phages) and parasitism by other mobile genetic elements (MGEs). Given the potent nuclease activity of CRISPR effectors, these enzymes must be carefully regulated to minimize toxicity and maximize anti-phage immunity. While attention has been given to the transcriptional regulation of these systems (reviewed in [1]), less consideration has been given to the crucial post-translational processes that govern enzyme activation and inactivation. Here, we review recent findings that describe how Cas nucleases are controlled in diverse systems to provide a robust anti-viral response while limiting auto-immunity. We also draw comparisons to a distinct bacterial immune system, restriction-modification.

Hepatic artery aneurysm rupture: case report, imaging findings, and literature review

Hepatic artery aneurysm rupture is a rare condition that requires urgent diagnosis and treatment in order to avoid a potentially fatal outcome. The clinical presentation is often non-specific. The classic triad of abdominal pain, gastrointestinal hemorrhage, and obstructive jaundice occurs in less than one-third of cases. Physical examination is rarely helpful since bruits, masses or pulsations are infrequent. Radiologic imaging provides the best tool to early diagnosis. Angiography has historically been the gold standard of diagnosis and is needed prior to radiologic intervention. Computerized tomography, doppler ultrasound and even magnetic resonance imaging have all demonstrated visceral artery aneurysms with success. Conventional treatment has included surgical ligation and resection. More recently transcatheter embolization or even percutaneous transhepatic injection of thrombin has been successfully performed by the interventional radiologist. This article discusses the clinical presentation, imaging findings, and review of the literature of this elusive entity.