Biology subjects

Neufeldt, C.

Publications and source records attributed to Neufeldt, C..

3 recordsLinked to original sources

bioRxiv2026

Comparative analysis of flavivirus sfRNA dynamics and secondary structure

The accumulation of subgenomic flavivirus RNAs (sfRNAs) modulates viral fitness and pathogenicity in culture and in vivo. These noncoding RNAs are produced by incomplete digestion of the flavivirus genome by the cellular 5-3 exoribonuclease (XRN1). Diverse flaviviruses have conserved RNA structural elements (RSEs) that map to their 3-untranslated region (3-UTR): Xrn-resistant RNA structures, dumbbell structures, and a 3-stem loop (3SL). Despite the importance of the 3-UTR RSEs for flavivirus replication, the structural dynamics of sfRNA during flavivirus infection are understudied. Here, we use digital droplet PCR to quantify sfRNA levels during infection for a panel of mosquito-borne flaviviruses (MbFV) including dengue virus serotypes 1 (DENV1), 2 (DENV2), and 4 (DENV4), and Zika virus (ZIKV). We then used SHAPE-MaP on XRN1-digested, in vitro-transcribed sfRNAs from each virus to determine their secondary structures compared to the corresponding sfRNAs obtained from flavivirus-infected A549 cells. Results seen in-cell and in vitro were largely similar; however, motifs within the dumbbell, the small hairpin (sHP) directly upstream of the 3-SL, and 3-SL regions showed significant differences in the extent of nucleotide reactivity. These differences were consistent among the four flaviviruses examined and may indicate regions of sfRNA that are shielded by interaction with proteins or other nucleic acids during infection. However, strong protection indicative of sustained interaction was not apparent. Our findings suggest that sfRNA interactions with viral and host factors within the cell are few, occur via base-paired regions, or are highly transient. ImportanceFlaviviruses are highly prevalent human pathogens. The flavivirus genome contains RNA structural elements (RSEs), including those encoded in the 3-UTR, that are necessary for viral replication. Subgenomic flavivirus RNAs (sfRNAs) are produced by incomplete digestion of flavivirus genomic RNA due to the cellular exoribonuclease XRN1 encountering 3-UTR RSEs that promote its stalling and disassociation. Viruses unable to produce sfRNAs are highly attenuated, underlining their biological importance. sfRNA secondary structure has been investigated previously but little information is available on sfRNA secondary structure dynamics in infected cells. By comparing SHAPE-MaP reactivities in vitro and in cells, we determined that previously inferred structures are likely maintained within infected cells. We also identified differences in the extent of SHAPE reactivity between in vitro and in-cell environments that were common to multiple mosquito-borne flaviviruses. These differences suggest that sfRNAs may engage in transient interactions within the cell that may be important for their function.

microbiology↗

bioRxiv2025

Homotypic endoplasmic reticulum membrane tethering is critical for flavivirus replication

Flaviviruses (genus Orthoflavivirus) are arthropod-borne viruses which cause approximately 400 million annual global infections in humans. Flavivirus infection requires cellular machinery to facilitate replication and spread. All known flaviviruses replicate in association with the host endoplasmic reticulum (ER), where genome replication is confined within virus-induced ER invaginations called viral replication organelles (vROs). Despite the central role of these structures during flavivirus infection, the mechanisms underlying vRO biogenesis remain undefined - particularly the membrane rearrangements required for their formation. In this work, we report a conserved role for a cellular ER remodeling protein, atlastin-2 (ATL2), in the organization of vROs within infected cells. Using confocal and electron microscopy, we show that ATL2 depletion leads to a reduction in vRO spatial distribution in flavivirus-infected cells. Changes in vRO distribution corresponded with a decrease in virus production and robust induction of innate immune responses. We also demonstrate that ATL2 accumulates in areas of vRO formation during flavivirus infection. Critically, mutational analysis showed that a tethering-competent but fusion-defective ATL2 mutant was sufficient to rescue DENV and ZIKV replication in ATL2-knockout cells. Finally, inhibition of ATL2 activity using synthetic peptides significantly reduced DENV replication in both immortalized and human primary cells, suggesting a possible avenue for targeting host ER functions to limit flavivirus replication. Taken together, these results show that membrane tethering plays a critical and conserved role in flavivirus infection, functioning to organize membranes for vRO biogenesis and limit cellular immune activation. Importantly, we provide evidence that ATL2-mediated membrane organization can be targeted to inhibit viral replication.

microbiology↗

bioRxiv2017

Induction of differentiation and metabolic reprogramming in human hepatoma cells by adult human serum

Tissue culture medium routinely contains fetal bovine serum (FBS). Here we show that culturing human hepatoma cells in their native, adult serum (human serum, HS) results in the restoration of key morphological and metabolic features of normal liver cells. When moved to HS, these cells show differential transcription of 22-32% of the genes, stop proliferating, and assume a hepatocyte-like morphology. Metabolic analysis shows that the Warburg-like metabolic profile, typical for FBS-cultured cells, is replaced by a diverse metabolic profile consistent with in vivo hepatocytes. We demonstrate the formation of large lipid and glycogen stores, increased glycogenesis, increased {beta}-oxidation, increased ketogenesis, and decreased glycolysis. Finally, organ-specific functions are restored, including xenobiotics degradation and secretion of bile, very low density lipoprotein, and albumin. Thus, organ-specific functions are not necessarily lost in cell cultures, but might be merely suppressed in FBS. Together, we showed that cells that are representative of normal physiology can be produced from cancer cells simply by replacing FBS by HS in culture media. The effect of serum is often overseen in cell culture and we provide a detailed study in the changes that occur, provide insight in some of the serum components that may play a role in the establishment of the different phenotypes, and discuss how these finding might be beneficial to a variety of research fields.

cell biology↗