Fully functional, naturally occurring and C-terminally truncated variant human immunodeficiency virus (HIV) Vif does not bind to HIV Gag but influences intermediate filament structure

A variant human immunodeficiency virus type 1 (HIV- 1) vif gene, vifA45-2, which encodes a protein lacking 19 amino acids at the C terminus but which is fully functional in supporting HIV replication in non-permissive cells h as been described previously. By employing newly generated anti-VifA45 seru m, further properties of VifA45 and its full-length counterpart, VifA45open , in comparison to Vif from HIV strain BH10 are reported in permissive HeLa and COS-7 cells. The results obtained using confocal microscopic localizat ion studies and in vitro binding assays do not support a requirement for th e direct interaction of HIV Gag with Vif. Furthermore and in contrast to pr evious conclusions, detergent solubility analyses do not demonstrate a role for the C terminus of Vif in mediating localization to the fraction contai ning cellular membrane proteins. Localization of Vif from HIV strain BH10 t o perinuclear aggregates in a small fraction (about 10%) of transfected HeL a cells has been previously reported. The intermediate filament protein vim entin colocalizes to these structures. In contrast, VifA45 and VifA45open f orm perinuclear aggregates in nearly all transfected HeLa cells; vimentin a s well as the cytoskeletal-bridging protein plectin, but not the microtubul ar protein tubulin, become relocalized to these structures. Interestingly, in COS-7 cells, all of the functional Vif proteins tested (Vif from strain BH10, VifA45 and VifA45open) predominantly localize in the cytoplasm but st ill induce dramatic aggregation of vimentin and plectin, i.e. in these cell s the respective Vif proteins are influencing intermediate filament structu re in the absence of colocalization.