Expression of ubiquitin, actin, and actin-like genes in African swine fever virus infected cells.

Northern blot hybridisation was used to study the accumulation of specific cellular mRNAs (ubiquitin and actin) in Vero cells infected with African swine fever virus (ASFV). ASFV modulates the cytoplasmic levels of ubiquitin and actin mRNAs throughout infection. Before viral DNA replication, degradation of ubiquitin mRNAs is dependent on de novo protein synthesis, since treatment with cycloheximide (CH) allowed the accumulation of ubiquitin mRNAs, while treatment with cytosine arabinoside (araC) induced a reduction in ubiquitin transcripts. Nevertheless, viral DNA replication is essential to the final increase observed in ubiquitin mRNA degradation. Furthermore, ubiquitin transcription seems to be tightly related to viral gene transcription, since before viral DNA replication ubiquitin and viral transcripts accumulate at opposite rates. Concerning actin transcription, the first step in actin mRNA degradation does not depend on de novo protein synthesis, since treatment with CH induced a reduction in actin mRNA. The second step in actin mRNA degradation, similarly to ubiquitin, depends on viral DNA replication. Finally, in the present study it has also been shown that ASFV codifies for actin-like genes. This is the first report of a virus encoding an actin-like gene.