Drawing on disorder: How viruses use histone mimicry to their advantage

Tarakhovsky, Alexander; Prinjha, Rab K.

In addition to the histone mimicry by NS1, a few other examples of viral histone mimicry have been described (King et al., 2016) . The insect polydnavirus Cotesia plutellae bracovirus (CpBV) encodes an orthologue of the insect histone H4 (CpBV-H4; that enables the wasp to parasitize its host, the diamondback moth, Plutella xylostella. The life cycle of C. plutellae requires colonization of young larvae of P. xylostella, which display growth retardation and immunosuppression once parasitized. These phenotypic changes are mediated by CpBV-H4, which is highly homologous to the host histone H4 and is additionally equipped with an extended lysine-rich 38-residue-long N-terminal tail. CpBV-H4 suppresses host immunity by inhibiting expression of genes encoding phenoloxidase and other antimicrobial peptides (Hepat and Kim, 2011) , and causes developmental retardation by inhibiting expression of insulin-like peptide in host larvae. CpBV-H4 affects host chromatin by joining eukaryotic nucleosomes , the epigenetic impact of which is gene expression changes affecting nearly 20% of the moth genome (Kumar et al., 2017) . Notably, the gene expression and phenotypic alterations mediated by CpBV-H4 depend completely on its lysine-rich N-terminal tail .