Résumé
Viral suppressors of RNA interference (VSRs) target host gene silencing pathways, thereby operating important roles in the viral cycle and in host cells, in which they counteract host innate immune responses. However, the molecular mechanisms of VSRs are poorly understood. We provide here biochemical and biophysical features of the dual suppressor/activator VSR P1 protein encoded by the rice yellow mottle virus. In silico analyses of P1 suggested common features with zinc finger proteins and native mass spectrometry unambiguously confirmed that recombinant P1 binds reversibly two zinc atoms, each with a different strength. Additionally, we demonstrate that the reaction of P1 with H2O2 leads to zinc release, disulfide bond formation, and protein oligomerization. A reversible protein modification by redox alterations has only been described for a limited number of zinc finger proteins and has never been reported for VSRs. Those reported here for P1 might be a general feature of Cys-rich VSRs and could be a key regulatory mechanism for the control of RNA silencing.
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► Viral suppressors block cellular antiviral RNAi but little is known about their biochemical properties. ► The Cys-rich viral suppressor P1 binds two zinc atoms in a redox-dependent manner. ► Zinc release from P1 occurs upon oxidation and is a reversible process. ► P1 oxidation is accompanied by oligomerization and conformational changes. ► Redox switches in Cys-rich viral suppressors of RNAi could be a key regulatory mechanism to generate structural polymorphism and for the control of RNA silencing.