Biology subjects

Tartell, M. A.

Publications and source records attributed to Tartell, M. A..

4 recordsLinked to original sources

bioRxiv2026

Genetic innovation in coronaviruses driven by a viral nuclease

Genetic variation in viruses is well known to arise from polymerase-driven nucleotide misincorporation. However, insertion and deletion (indel) mutations that occur at lower, largely unknown, frequencies can underly more dramatic phenotypic changes that emerge when advantageous. Using a human coronavirus (HCoV-OC43) construct that reports rare indel mutations, we show that non-structural protein-15 (NSP15), a nuclease encoded by coronaviruses, can drive the acquisition of a class of insertion mutations. Ultra-deep sequencing of both HCoV-OC43 and SARS-CoV-2 populations reveals a similar requirement for NSP15 during insertion mutant generation. Overall, the insertional mutation frequency exceeded 10-3/genome in these two coronaviruses. Analysis of thousands of HCoV-OC43 and SARS-CoV-2 insertion mutants reveals a mutational process in which NSP15 cuts viral RNA, yielding oligonucleotides that correspond to inserts that are acquired at distal genomic locations. The presence of an insertion mutation at the S1/S2 junction in the SARS-CoV-2 spike protein that generates a furin cleavage site and enhances viral transmissibility, may have been necessary for enabling the COVID19 pandemic. We found numerous examples of potential furin cleavage site acquisition and replacement through insertion mutation during the normal course of coronavirus replication. Such events are, therefore, likely commonplace in coronavirus populations of a size that occurs in nature.

microbiology↗

bioRxiv2026

Interferon-gamma induced RNF213 targets nascent double membrane vesicles to inhibit coronavirus primary translation

Innate immune systems employ many mechanisms to inhibit the replication of viruses that profoundly affect host range and pathogenicity. To identify proteins that restrict human respiratory virus replication, we executed CRISPR screens targeting both type-I and type-II interferon stimulated genes. Among the candidate antiviral genes identified, the giant ring finger protein 213 (RNF213) was a key mediator of antiviral activity of interferon gamma (IFN{gamma}) against the human betacoronavirus HCoV-OC43. RNF213 has ATPase and ubiquitin ligase activities, both of which were required for anti-HCoV-OC43 activity. Using newly designed reporter viruses, we demonstrate that RNF213 acts by a previously undescribed mechanism, inhibiting the translation of incoming viral genomes. RNF213 colocalized and coimmunoprecipitated with the primary viral translation product, NSP3, that orchestrates the formation coronavirus replication compartments. Notably, RNF213 restricted genetically diverse common human coronaviruses, but SARS-CoV-2 apparently evades interaction with and inhibition by RNF213.

microbiology↗

bioRxiv2020

Messenger RNA cap methylation by PCIF1 attenuates the interferon-β induced antiviral state

Interferons induce cell intrinsic responses associated with resistance to viral infection. To overcome the suppressive action of interferons and their downstream effectors viruses have evolved diverse mechanisms. Working with vesicular stomatitis virus (VSV) we report a role for the host cell N6-adenosine mRNA cap-methylase, phosphorylated C-terminal domain interacting factor 1 (PCIF1), in attenuating the antiviral activity of interferon-{beta}. Using cell based and in vitro biochemical assays we demonstrate that PCIF1 efficiently modifies VSV mRNA cap structures to m7Gpppm6Am, and we identify the cis-acting elements required for this modification. Under basal conditions, N6-methylation of VSV mRNA cap structures is functionally inert with regard to mRNA stability, translation and viral infectivity. Induction of an antiviral state by treatment of cells with interferon-{beta} prior to infection uncovered a functional role for PCIF1 in attenuation of the antiviral response. Cells lacking PCIF1 or expressing a catalytically inactive PCIF1, exhibit an augmented effect of interferon-{beta} in the inhibition of viral replication and gene expression. This work identifies a function of PCIF1 and cap-proximal m6Am in attenuation of the host response to VSV infection that likely extends to other viruses. SignificanceThe cap structure present at the 5 end of eukaryotic mRNAs regulates RNA stability, translation, and marks mRNA as self, thereby impeding recognition by the innate immune system. Cellular transcripts beginning with adenosine are additionally modified at the N6 position of the 2-O methylated cap-proximal residue by the methyltransferase PCIF1 to m7Gpppm6Am. We define a function for this N6-adenosine methylation in attenuating the interferon-{beta} mediated suppression of viral infection. Cells lacking PCIF1, or defective in its enzymatic activity, augment the cell intrinsic suppressive effect of interferon-{beta} treatment on vesicular stomatitis virus gene expression. VSV mRNAs are efficiently methylated by PCIF1, suggesting this contributes to viral evasion of innate immune suppression.

microbiology↗

bioRxiv2020

Neutralizing antibody and soluble ACE2 inhibition of a replication-competent VSV-SARS-CoV-2 and a clinical isolate of SARS-CoV-2.

Antibody-based interventions against SARS-CoV-2 could limit morbidity, mortality, and possibly disrupt epidemic transmission. An anticipated correlate of such countermeasures is the level of neutralizing antibodies against the SARS-CoV-2 spike protein, yet there is no consensus as to which assay should be used for such measurements. Using an infectious molecular clone of vesicular stomatitis virus (VSV) that expresses eGFP as a marker of infection, we replaced the glycoprotein gene (G) with the spike protein of SARS-CoV-2 (VSV-eGFP-SARS-CoV-2) and developed a high-throughput imaging-based neutralization assay at biosafety level 2. We also developed a focus reduction neutralization test with a clinical isolate of SARS-CoV-2 at biosafety level 3. We compared the neutralizing activities of monoclonal and polyclonal antibody preparations, as well as ACE2-Fc soluble decoy protein in both assays and find an exceptionally high degree of concordance. The two assays will help define correlates of protection for antibody-based countermeasures including therapeutic antibodies, immune {gamma}-globulin or plasma preparations, and vaccines against SARS-CoV-2. Replication-competent VSV-eGFP-SARS-CoV-2 provides a rapid assay for testing inhibitors of SARS-CoV-2 mediated entry that can be performed in 7.5 hours under reduced biosafety containment.

microbiology↗