Functional Analyses of the Histone-like A104R Protein of African Swine Fever Virus and of a Homologous Pseudogene Product Found in Soft Tick Genomes.

Abstract

African swine fever virus (ASFV) causes a fatal disease in domestic pigs and wild boars (), leading to nearly 100% mortality during acute infection and significant economic losses in swine production. Unlike other eukaryotic viruses, ASFV encodes a histone-like nucleic acid-binding protein, pA104R, which is highly conserved and present in all described ASFV isolates of different genotypes. Moreover,-like sequences have been identified in the genomes of soft ticks, which can replicate and transmit ASFV. Using a virulent genotype IX field isolate from Kenya, we analyzed the importance offor viral replication in a permissive wild boar cell line (WSL). In this study, we confirmed thatis not essential for in vitro replication of ASFV. Loss ofdid not detectably affect viral DNA replication or RNA transcription but led to a moderate reduction in virus titers and plaque sizes. Substitution ofwith a similar ASFV-like element derived from the genome of ansoft tick was not capable of rescuing the deletion mutant phenotype. In contrast, reintroduction of the authenticopen reading frame (ORF) into the deletion mutant fully restored wild-type virus growth properties. In accompanying studies, we verified the DNA-binding activities of the ASFV- and tick-derived A104R proteins and performed mass spectrometric analyses of the pA104R interactome. These experiments revealed, besides DNA-dependent co-precipitated proteins, specific DNA-independent protein-protein interactions of pA104R with other viral and cellular proteins.