HIGHLY LOCALIZED TRACKS OF HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 NEF INTHE NUCLEUS OF CELLS OF A HUMAN CD4-CELL LINE( T)

A human T-cell line constitutively expressing the nef gene from the hu man immunodeficiency virus type 1 SF2 isolate was used to examine the distribution of the Nef protein in the nucleus. High-resolution immuno gold labeling/electron microscopic studies with polyclonal anti-Nef an tibodies on nef+ and nef- cells revealed that a small fraction of Nef is in the nucleus and it is localized in specific curvilinear tracks t hat extend between the nuclear envelope and the nucleoplasm. An examin ation of the sequence of the SF2 nef gene revealed a putative nuclear targeting sequence that was previously found in several other eukaryot ic nucleoplasmic proteins. The nuclear localization of Nef suggests a potential nuclear function for this protein. The presence of Nef in di stinct nuclear tracks suggests that Nef is transported along a specifi c pathway that extends from the nuclear envelope into the nucleoplasm. A previous study [Meie U. T. & Blobel, G. (1992) Cell 70, 127-138] ha s shown that the nucleolar protein of rat liver cells (Nopp140) shuttl es from the nucleolus to the nuclear envelope on distinct tracks. The present study has suggested that the transport of a nucleoplasmic prot ein may also occur on distinct nuclear pathways.