Role of the cytoskeleton in nuclear import.

The role of the cytoskeleton in regulating the intracellular localization of cellular organelles, viruses, and individual proteins has been the subject of much investigation in recent years. While regulated transport through the nuclear pore remains the primary determinant of nuclear localization, it has become clear that the nuclear localization of viruses and some cellular proteins is mediated by the ability of the cytoskeleton, usually microtubules, to direct their perinuclear accumulation in close proximity to the nuclear pore complex. We also discuss how the size of virions and the viscous nature of the cytoplasm would make it very unlikely or even impossible for viruses to achieve this localization by diffusion alone in the absence of active transport mechanisms. This review focuses on the known methods employed by different viruses and proteins to effect their perinuclear accumulation.