Biology subjects

Schafer, X.

Publications and source records attributed to Schafer, X..

4 recordsLinked to original sources

bioRxiv2025

Cellular antibody affinity-based CRISPR Screening identifies JUNB as a broadly acting anti-viral factor

CRISPR screening is a powerful approach to identify genetic perturbations that impact viral infection. However, most virus-focused CRISPR screens utilize selection strategies that limit the ability to identify genes important for infection. Here, we developed a novel CRISPR screening pipeline to identify cellular determinants of Human Cytomegalovirus infection based on virally induced remodeling of cellular antibody affinity (VIRCAA), which is scalable for large libraries and can identify cellular genes that impact HCMV infection at different life cycle stages. We utilized this pipeline to interrogate proteomic and transcriptomic data sets associated with the HCMV UL26 protein, which blocks anti-viral signaling during infection. We find that JUNB drives anti-viral gene expression, induces protein ISGylation, and suppresses diverse viral infections. Further, UL26 proximally interacts with JUNB and suppresses JUNBs nuclear condensation and JUNB-mediated contraction of viral DNA replication compartments. These results highlight the VIRCAA pipelines utility for identifying important determinants of viral infection.

molecular biology↗

bioRxiv2023

Cytomegalovirus-induced inactivation of TSC2 disrupts the coupling of fatty acid biosynthesis to glucose availability resulting in a vulnerability to glucose limitation

Human cytomegalovirus (HCMV) modulates cellular metabolism to support productive infection, and the HCMV UL38 protein drives many aspects of this HCMV-induced metabolic program. However, it remains to be determined whether virally-induced metabolic alterations might induce novel therapeutic vulnerabilities in virally infected cells. Here, we explore how HCMV infection and the UL38 protein modulate cellular metabolism and how these changes alter the response to nutrient limitation. We find that expression of UL38, either in the context of HCMV infection or in isolation, sensitizes cells to glucose limitation resulting in cell death. This sensitivity is mediated through UL38s inactivation of the TSC complex subunit 2 (TSC2) protein, a central metabolic regulator that possesses tumor-suppressive properties. Further, expression of UL38 or the inactivation of TSC2 results in anabolic rigidity in that the resulting increased levels of fatty acid biosynthesis are insensitive to glucose limitation. This failure to regulate fatty acid biosynthesis in response to glucose availability sensitizes cells to glucose limitation, resulting in cell death unless fatty acid biosynthesis is inhibited. These experiments identify a regulatory circuit between glycolysis and fatty acid biosynthesis that is critical for cell survival upon glucose limitation and highlight a metabolic vulnerability associated with viral infection and the inactivation of normal metabolic regulatory controls. ImportanceViruses modulate host cell metabolism to support the mass production of viral progeny. For Human Cytomegalovirus, we find that the viral UL38 protein is critical for driving these pro-viral metabolic changes. However, our results indicate that these changes come at a cost, as UL38 induces an anabolic rigidity that leads to a metabolic vulnerability. We find that UL38 decouples the link between glucose availability and fatty acid biosynthetic activity. Normal cells respond to glucose limitation by down-regulating fatty acid biosynthesis. Expression of UL38 results in the inability to modulate fatty acid biosynthesis in response to glucose limitation, which results in cell death. We find this vulnerability in the context of viral infection, but this linkage between fatty acid biosynthesis, glucose availability, and cell death could have broader implications in other contexts or pathologies that rely on glycolytic remodeling, for example, oncogenesis.

microbiology↗

bioRxiv2022

Human Cytomegalovirus induces neuronal enolase to support virally-mediated metabolicremodeling

Viruses depend on cellular metabolic resources to supply the energy and biomolecular building blocks necessary for their replication. Human Cytomegalovirus (HCMV), a leading cause of birth defects and morbidity in immunosuppressed individuals, induces numerous metabolic activities that are important for productive infection. However, many of the mechanisms through which these metabolic activities are induced and how they contribute to infection are unclear. We find that HCMV infection of fibroblasts induces a neuronal gene signature, as well as the expression of several metabolic enzyme isoforms that are typically expressed in other tissue types. Of these, the most substantially induced gene was the neuron-specific isoform of enolase (ENO2). Induction of ENO2 expression is important for HCMV-mediated glycolytic activation, as well as for the virally-induced remodeling of pyrimidine-sugar metabolism, which provides the glycosyl subunits necessary for protein glycosylation. Inhibition of ENO2 expression or activity reduced UDP-sugar pools, attenuated the accumulation of viral glycoproteins, and induced the accumulation of non-infectious viral particles. In addition, our data indicate that the induction of ENO2 expression depends on the HCMV UL38 protein. Collectively, our data indicate that HCMV infection induces a tissue atypical neuronal glycolytic enzyme to activate glycolysis and UDP-sugar metabolism to provide the glycosyl building blocks necessary for viral protein glycosylation and the production of infectious virions. Significance StatementViruses are obligate parasites that obtain energy and mass from their host cell. Control over the metabolic resources of the cell has emerged as an important host-pathogen interaction that can determine infectious outcomes. We find that the Human Cytomegalovirus (HCMV), a major cause of birth defects and morbidity in immunosuppressed patient populations, induces a neuronal gene signature in fibroblasts including the expression of neuronal-specific enolase (ENO2). Our data indicate that ENO2 is important for HCMV-mediated metabolic remodeling including glycolytic activation and the production of pyrimidine sugars, as well as for viral infectivity. These findings indicate that viruses are capable of tapping into alternative tissue-specific metabolic programs to support infection, highlighting an important viral mechanism of metabolic modulation.

microbiology↗

bioRxiv2017

Potential Mechanisms Linking SIRT Activity And Hypoxic 2-Hydroxyglutarate Generation: No Role For Direct Enzyme (De)acetylation

2-hydroxyglutarate (2-HG) is a hypoxic metabolite with potentially important epigenetic signaling roles. The mechanisms underlying 2-HG generation are poorly understood, but evidence suggests a potential regulatory role for the sirtuin family of lysine deacetylases. Thus, we hypothesized that the acetylation status of the major 2-HG-generating enzymes (isocitrate dehydrogenase (IDH), malate dehydrogenase (MDH) and lactate dehydrogenase (LDH)) may govern their 2-HG generating activity. In-vitro acetylation of these enzymes, with confirmation by western blotting, mass spectrometry, and reversibility by incubation with recombinant sirtuins, yielded no effect on 2-HG generating activity. In addition, while elevated 2-HG in hypoxia is associated with the activation of lysine deacetylases, we found that mice lacking mitochondrial SIRT3 exhibited hyperacetylation and elevated 2-HG. These data suggest there is no direct link between enzyme acetylation and 2-HG production. Furthermore, our observed effects of in-vitro acetylation on the canonical activities of IDH, MDH and LDH appeared to contrast sharply with previous findings wherein acetyl-mimetic lysine mutations resulted in inhibition of these enzymes. Overall these data suggest that a causal relationship should not be assumed, between acetylation of metabolic enzymes and their activities, canonical or otherwise.

biochemistry↗