Cellular LITAF interacts with frog virus 3 75L protein and alters its subcellular localization.

Iridoviruses are a family of large double-stranded DNA (dsDNA) viruses that are composed of 5 genera, including the Lymphocystivirus, Ranavirus, Megalocytivirus, Iridovirus, and Chloriridovirus genera. The frog virus 3 (FV3) 75L gene is a nonessential gene that is highly conserved throughout the members of the Ranavirus genus but is not found in other iridoviruses. FV3 75L shows high sequence similarity to a conserved domain found in the C terminus of LITAF, a small cellular protein with unknown function. Here we show that FV3 75L localizes to early endosomes, while LITAF localizes to late endosomes/lysosomes. Interestingly, when FV3 75L and LITAF are cotransfected into cells, LITAF can alter the subcellular localization of FV3 75L to late endosomes/lysosomes, where FV3 75L then colocalizes with LITAF. In addition, we demonstrated that virally produced 75L colocalizes with LITAF. We confirmed a physical interaction between LITAF and FV3 75L but found that this interaction was not mediated by two PPXY motifs in the N terminus of LITAF. Mutation of two PPXY motifs in LITAF did not affect the colocalization of LITAF and FV3 75L but did change the location of the two proteins from late endosomes/lysosomes to early endosomes.