Murine cytomegalovirus IE3‐dependent transcription is required for DAI/ZBP1‐mediated necroptosis

Abstract

DNA-dependent activator of interferon regulatory factors/Z-DNA binding protein 1 (DAI/ZBP1) is a crucial sensor of necroptotic cell death induced by murine cytomegalovirus (MCMV) in its natural host. Here, we show that viral capsid transport to the nucleus and subsequent viral IE3-dependent early transcription are required for necroptosis. Necroptosis induction does not depend on input virion DNA or newly synthesized viral DNA A putative RNA-binding domain of DAI/ZBP1, Zα2, is required to sense virus and trigger necroptosis. Thus, MCMV IE3-dependent transcription from the viral genome plays a crucial role in activating DAI/ZBP1-dependent necroptosis. This implicates RNA transcripts generated by a large double-stranded DNA virus as a biologically relevant ligand for DAI/ZBP1 during natural viral infection.

Live and let die: ZBP1 senses viral and cellular RNAs to trigger necroptosis

“…In two recent articles published in EMBO Reports and The EMBO Journal (Maelfait et al , ; Sridharan et al , ), the authors investigated the mechanism of ZBP1‐mediated activation of necroptosis by MCMV infection (Fig ). Since the WT virus efficiently blocks this mechanism by the expression of M45, they studied a previously characterized MCMV expressing a mutated form of M45 (MCMV‐M45 mutRHIM ) that fails to inhibit necroptosis.…”

“…Since the WT virus efficiently blocks this mechanism by the expression of M45, they studied a previously characterized MCMV expressing a mutated form of M45 (MCMV‐M45 mutRHIM ) that fails to inhibit necroptosis. By mutating or deleting ZBP1 ZBDs, the authors uncovered a crucial role of nucleic acid binding function of ZBP1 in MCMV‐M45 mutRHIM ‐induced necroptosis (Maelfait et al , ; Sridharan et al , ). Sridharan et al () reported that although deletion of Zα1 and Zα2 ZBP1 ZBDs decreased cell death induced by MCMV‐M45 mutRHIM , point mutations in these domains of residues critical for ZBP1 interaction with nucleic acids delayed cell death but did not significantly inhibit it.…”

“…By mutating or deleting ZBP1 ZBDs, the authors uncovered a crucial role of nucleic acid binding function of ZBP1 in MCMV‐M45 mutRHIM ‐induced necroptosis (Maelfait et al , ; Sridharan et al , ). Sridharan et al () reported that although deletion of Zα1 and Zα2 ZBP1 ZBDs decreased cell death induced by MCMV‐M45 mutRHIM , point mutations in these domains of residues critical for ZBP1 interaction with nucleic acids delayed cell death but did not significantly inhibit it. Conversely, mutations of these same residues by Maelfait et al () prevented virus‐induced necroptosis.…”

“…These discrepancies might be due to differences in the mutations performed in these two studies, as well as in distinct cell lines used. Moreover, Sridharan et al () speculated that alternative ZBP1 ZBDs functions, other than nucleic acid binding, could also participate to virus‐induced necroptosis.…”

“…Surprisingly, Maelfait et al () showed in infected cells that ZBP1 directly bound via its ZBDs to newly synthesized RNAs but not viral DNA. Moreover, both papers showed that MCMV‐M45 mutRHIM ‐induced necroptosis required RNA synthesis but not viral DNA replication (Maelfait et al , ; Sridharan et al , ). Interestingly, MCMV immediate‐early protein 3 (IE3) protein, essential for the transcription of viral genes, played a crucial role in this mechanism (Maelfait et al , ; Sridharan et al , ).…”