CASP3 and infection: The authors used the elegant approach of converting the apoptosis phenotype of active caspase-3 expression after infection with mCMV-ΔM36 by blocking apoptotic signaling not only by reinsertion of M36 in virus mCMV-ΔM36-Rev, which restitutes both the block in apoptosis and putative other functions of M36, but alternatively also earlier in the signaling cascade by viral expression of a dominant-negative (DN) mutation of FADD (FADDDN) restituting the block in apoptosis selectively (Fig 4A).