ORF10–Cullin-2–ZYG11B complex is not required for SARS-CoV-2 infection

Significance

Understanding the functions of the genes encoded in the SARS-CoV-2 genome is imperative to understanding its pathogenesis. One unique feature of the SARS-CoV-2 genome is ORF10, a small putative protein that was hypothesized to promote infection by hijacking a cellular E3 ubiquitin ligase, CRL2 ^ZYG11B. Here, we investigate whether ORF10 hijacks CRL2 ^ZYG11B or functions in other ways, such as to inhibit CRL2 ^ZYG11B or be degraded by it. We do not find evidence that ORF10 regulates or is regulated by CRL2 ^ZYG11B, and, furthermore, we find that ZYG11B and its paralog are dispensable for SARS-CoV-2 infection in cultured cells.

Abstract

In order to understand the transmission and virulence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), it is necessary to understand the functions of each of the gene products encoded in the viral genome. One feature of the SARS-CoV-2 genome that is not present in related, common coronaviruses is ORF10, a putative 38-amino acid protein-coding gene. Proteomic studies found that ORF10 binds to an E3 ubiquitin ligase containing Cullin-2, Rbx1, Elongin B, Elongin C, and ZYG11B (CRL2 ^ZYG11B). Since CRL2 ^ZYG11B mediates protein degradation, one possible role for ORF10 is to “hijack” CRL2 ^ZYG11B in order to target cellular, antiviral proteins for ubiquitylation and subsequent proteasomal degradation. Here, we investigated whether ORF10 hijacks CRL2 ^ZYG11B or functions in other ways, for example, as an inhibitor or substrate of CRL2 ^ZYG11B. While we confirm the ORF10−ZYG11B interaction and show that the N terminus of ORF10 is critical for it, we find no evidence that ORF10 is functioning to inhibit or hijack CRL2 ^ZYG11B. Furthermore, ZYG11B and its paralog ZER1 are dispensable for SARS-CoV-2 infection in cultured cells. We conclude that the interaction between ORF10 and CRL2 ^ZYG11B is not relevant for SARS-CoV-2 infection in vitro.