As part of their replication strategy, viruses can use nucleolar components to favour viral transcription and translation, or alter the cell cycle [48, 49] . Western blot analysis indentified NS4 in the nuclear fraction of BTV infected cells, while immunofluorescence confocal microscopy co-localised NS4 to the nucleolus. GIV-NS4 showed sequence similarity to UTP20, a small subunit processome component and a component of the nucleolus. UTP20 is part of the U3 small nucleolar RNA (snoRNA) protein complex (U3 snoRNP) and is involved in 18S rRNA processing [53] . Whether NS4 interferes with the processing of the 18s rRNA remains to be clarified in future work.