Nuclear and nucleolar localization of an African swine fever virus protein, I14L, that is similar to the herpes simplex virus-encoded virulence factor ICP34.5

PCR analysis of the genomes of 18 different African swine fever virus (ASFV ) isolates showed that the l14L open reading frame (ORF) was present as eit her a long form or short form in all of the isolates. Sequencing of the ORF from eight isolates confirmed that both forms of the ORF were well conserv ed. Antisera raised against the l14L protein identified the long form of th e protein as a 21 kDa protein expressed late during ASFV infection. Immunof luorescent analysis of transiently expressed haemagglutinin-tagged forms of the l14L protein showed that the long form of the protein localized predom inantly to the nucleus and within the nucleoli, In contrast, although the s hort form of the protein was also present predominantly in the nucleus, it did not localize to the nucleoli. Deletion of the N-terminal 14 amino acids from the long form of the l14L protein, which includes a high proportion o f basic Arg/Lys residues, abolished the specific nucleolar localization of the protein, although the protein was still present in the nucleus. Additio n of this 14 amino acid sequence to beta-galactosidase or replacement of th e N-terminal 14 amino acids of the l14L short form with those from the long form directed both of these modified proteins to the nucleolus. This indic ates that this 14 amino acid sequence contains all the signals required for nucleolar localization.