Irrespective of the exact mechanism, the targeting of TIR adaptor proteins may represent H 89 in vivo a further mechanism underlying the inhibitory effects of

viral Pellino on TLR signalling. Viruses have evolved a wide range of immunoevasive strategies, including the targeting of key innate immune signalling pathways. Vaccinia virus A52R has been shown to inhibit TLR-mediated activation of NF-κB by disrupting signalling complexes containing TRAF6 and IRAK2 28. Furthermore, in a manner similar to the actions of viral Pellino on IRAK-1, MCMV M45 was found to bind RIP1, blocking its ubiquitination and thereby activation of NF-κB by TNF-α and TLR3 signalling 29. Here, we reveal the immunoevasive

properties of a poxviral Pellino homolog. This identifies the ability of an entomopoxvirus protein AZD2014 cell line to combat insect immunity. The ability of viral Pellino to also interfere with TLR signalling highlights the amazing conservation across the evolutionary divide of Toll and TLR signalling. An increased understanding of the mechanistic basis to the regulatory effects of viral Pellino may also provide a greater appreciation of the precise role of mammalian Pellinos in IL-1/TLR signalling. Viral Pellino was initially discovered based on the sequence identity with members of the mammalian Pellino family. However, the sequence identity was quite low and given that the X-ray structure of part of the Pellino2 protein had been recently resolved, we employed homology modelling to evaluate if the limited sequence identity has the potential to translate into shared structural properties. An intriguing picture emerges in which viral Pellino shares some of the structural characteristics of mammalian proteins but differs in other respects. Like some of CYTH4 its mammalian counterparts, it has a cytoplasmic localisation. This is hardly surprising since bioinformatic analysis failed to predict any

transmembrane domain or nuclear localisation sequences. Mammalian Pellinos possess two distinct domains; a N-terminal FHA domain that facilitates binding to phosphorylated IRAK-1 18 and a C-terminal RING-like domain that catalyses polyubiquitination of IRAK-1. Viral Pellino lacks the latter but appears to have the potential to form a FHA domain based on two sets of findings. First, homology modelling in conjunction with molecular dynamics indicates the potential for viral Pellino to form a stable 11-stranded β-sandwich that is characteristic of a canonical FHA domain. Second, viral Pellino shows conservation of the four signature amino acid residues in FHA domain-containing proteins that mediate direct binding to phosphorylated threonine residues on partner proteins.