Structural insights into the viral proteins binding by TRIM7 reveal a general C-terminal glutamine recognition mechanism

The E3 ligase TRIM7 has emerged as a critical player in viral infection and pathogenesis. A recent study found that TRIM7 inhibits human enteroviruses through ubiquitination and proteasomal degradation of viral 2BC protein by targeting the 2C moiety of 2BC protein. Here, we report the crystal structures of TRIM7 in complex with 2C, where the C-terminal region of 2C is inserted into a positively charged groove of the TRIM7 PRY-SPRY domain. Structure-guided biochemical studies revealed the C-terminus glutamine residue of 2C as the primary determinant for TRIM7 binding. Such a glutamine-end motif binding mechanism can be successfully extended to other substrates of TRIM7. More importantly, leveraged by this finding, we were able to identify norovirus and SARS-CoV-2 proteins, and physiological proteins, as new TRIM7 substrates. We further show that TRIM7 may function as a restriction factor to promote the degradation of the viral proteins of norovirus and SARS-CoV-2, thereby restoring the Type I interferon immune response and inhibiting viral infection. Several crystal structures of TRIM7 in complex with SARS-CoV-2 proteins are also determined, and a conserved C-terminus glutamine-specific interaction is observed. These findings unveil a common recognition mode by TRIM7, providing the foundation for further mechanistic characterization of antiviral and cellular functions of TRIM7.