Required for vesicle docking or fusion during acrosome biogenesis (By similarity). May play a role in RNA trafficking or localization. In case of infection by HIV-1, acts as a cofactor for viral Rev and promotes movement of Rev-responsive element-containing RNAs from the nuclear periphery to the cytoplasm. This step is essential for HIV-1 replication. Interacts with EPS15R and EPS15. Interacts with FCHO1. Ubiquitously expressed. Contains FG repeats. The FG repeat region is required for acting as a cofactor of HIV-1 Rev. O-glycosylated. Aberrant splicing within exon 1.