Structural and Hydrodynamic Characterization of Dimeric Human Oligoadenylate Synthetase 2

Abstract

Oligoadenylate synthetases (OASs) are a family of interferon-inducible enzymes that require double-stranded RNA (dsRNA) as a cofactor. Upon binding dsRNA, OAS undergoes a conformational change and is activated to polymerize ATP into 2′-5′-oligoadenylate chains. The OAS family consists of several isozymes, with unique domain organizations to potentially interact with dsRNA of variable length, providing diversity in viral RNA recognition. In addition, oligomerization of OAS isozymes, potentially OAS1 and OAS2, is hypothesized to be important for 2′-5′-oligoadenylate chain building. In this study, we present the solution conformation of dimeric human OAS2 using an integrated approach involving small-angle x-ray scattering, analytical ultracentrifugation, and dynamic light scattering techniques. We also demonstrate OAS2 dimerization using immunoprecipitation approaches in human cells. Whereas mutation of a key active-site aspartic acid residue prevents OAS2 activity, a C-terminal mutation previously hypothesized to disrupt OAS self-association had only a minor effect on OAS2 activity. Finally, we also present the solution structure of OAS1 monomer and dimer, comparing their hydrodynamic properties with OAS2. In summary, our work presents the first, to our knowledge, dimeric structural models of OAS2 that enhance our understanding of the oligomerization and catalytic function of OAS enzymes.

Molecular mechanism of quorum sensing inhibition in Streptococcus by the phage protein paratox

“…Since our complex structure includes only the DBD of ComR, we used a SEC-coupled SAXS setup to visualize the full ComR:Prx complex. SAXS provides low-resolution structural information that is useful for visualizing the overall shape of protein complexes in solution, including large conformational changes ( 28 ). SEC-SAXS datasets were collected for ComR, Prx, and the ComR:Prx complex, each in the same buffer (gel filtration buffer) at a concentration of 9 mg/ml ( Fig.…”

Generation of Cytotoxic T Cells and Dysfunctional CD8 T Cells in Severe COVID-19 Patients

“…We found equilibrated expression of ISGs such as ISG15, IRF7, STAT1, IFNA1, IFNA2, and IFNAR1 by PCR array in CD8+ T lymphocytes. We also evidenced an increase in the expression of OAS2 and Mx1 , which play an important role in defense against viral infections by catalyzing the synthesis of 2′-5′-oligoadenylate for the activation of RNase L [ 34 ] or inhibiting the infection by blocking viral transcription and replication, respectively [ 35 , 36 ]. It has been reported in SARS-CoV-2 infection that the virus can suppress the type I IFN response by evasion mechanisms such as ubiquitination of cytosolic sensors and inhibition of translocation of nuclear factors by decreasing STAT1 phosphorylation, among other mechanisms that are still not fully understood [ 19 , 37 , 38 ].…”

Molecular mechanism of quorum sensing inhibition in Streptococcus by the phage protein paratox

“…ComR:Prx complex Since our complex structure includes only the DNA binding domain of ComR, we used a SEC-coupled SAXS set-up to visualize the full ComR:Prx complex. SAXS provides lowresolution structural information that is useful for visualizing the overall shape of protein complexes in solution, including large conformational changes (28). SEC-SAXS datasets were collected for ComR, Prx and the ComR:Prx complex, each in the same buffer (gel filtration buffer) at a concentration of 9 mg/mL (Fig.…”