PARP9 and viral infectious disease: Next, given that DTX3L is an active E3 ubiquitin ligase (Takeyama et al, 2003; Zhu et al, 2022) and that PARP9 and DTX3L have been reported to regulate ubiquitination in response to viral infection (Zhang et al, 2015), we also investigated if we could observe any changes to ubiquitination after IFN treatment.