Characterization of the equine infectious anaemia virus S2 protein

S2 is an accessory protein of equine infectious anaemia virus (EIAV), the f unction of which is unknown. In order to gain insight into the function of S2, the intracellular localization of the protein, its interaction with vir al proteins and its incorporation into viral particles have been investigat ed. Immunolocalization of S2 revealed punctate staining in the cytoplasm an d the S2 protein coprecipitated with the EIAV Gag precursor. Despite overex pression of S2 through the use of a codon-optimized sequence, there was no preferential association of S2 with EIAV particles. These data suggest that S2 may function to organize the Gag protein during particle assembly in th e cytoplasm but that it is unlikely to be involved in the early stages of t he virus life-cycle.