N-terminal acetylation of the & beta;C1 protein encoded by the betasatellite of tomato yellow leaf curl China virus is critical for its viral pathogenicity

N-terminal acetylation (N-acetylation) is one of the most common protein modifications and plays crucial roles in viability and stress responses in animals and plants. However, very little is known about N-acetylation of viral proteins. Here, we identified the Thr residue at position 2 (Thr-2) in the I3C1 protein encoded by the betasatellite of tomato yellow leaf curl China virus (TYLCCNB-I3C1) as a novel N-acetylation site. Furthermore, the effects of TYLCCNB-I3C1 N-acetylation on its function as a pathogenicity factor were determined via N-acetylation mutants in Nicotiana benthamiana plants. We found that N-acetylation of TYLCCNB-I3C1 is critical for its self-interaction in the nucleus and viral pathogenesis, and that removal of N-acetylation of TYLCCNB-I3C1 attenuated tomato yellow leaf curl China virus-induced symptoms and led to accelerated degradation of TYLCCNB-I3C1 through the ubiquitin-proteasome system. Our data reveal a protective effect of N-acetylation of TYLCCNB-I3C1 on its pathogenesis and demonstrate an antagonistic crosstalk between N-acetylation and ubiquitination in this gem-iniviral protein.

Automated summary

N-terminal acetylation (N-acetylation) is a common protein modification in animals and plants, but little is known about its role in viral proteins. In this study, the Thr-2 residue in the I3C1 protein encoded by the betasatellite of tomato yellow leaf curl China virus (TYLCCNB-I3C1) was identified as a novel N-acetylation site. The study revealed that N-acetylation of TYLCCNB-I3C1 is critical for its nuclear self-interaction and viral pathogenesis. Removal of N-acetylation attenuated symptoms induced by tomato yellow leaf curl China virus and accelerated degradation of TYLCCNB-I3C1 through the ubiquitin-proteasome system, demonstrating an antagonistic crosstalk between N-acetylation and ubiquitination in this viral protein.