Here we describe an African swine fever virus (ASFV) protein encoded by the open reading frame 5-AR that shares structural and functional similarities with the family of bacterial histone-like proteins which include histone-like DNA binding proteins, integration host factor, and Bacillus phage SPO1 transcription factor, TF1. The ASFV 5-AR gene was cloned by PCR and expressed in E. coli. Monospecific antiserum prepared to the 5-AR bacterial expression product specifically immunoprecipitated a protein of approximately 11.6kDa from ASFV infected swine macrophages at late times post-infection. Additionally, the 5-AR expression product was strongly recognized by ASFV convalescent pig serum, indicating its antigenicity during natural infection. Cloned p11.6 bound both double and single stranded DNA-cellulose columns. Consistent with a DNA binding function, immunoelectronmicroscopy localized p11.6 to the virion nucleoid. To our knowledge, p11.6 is the first bacterial histone-like DNA-binding protein found in an animal virus or eukaryotic cell system.
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