The primary aim of HIV at initial infection of a cell is to rapidly deliver its RNA genome to the nucleus for integration into the host DNA. To get there, its large virion particles must first navigate through the cytoplasm towards the nuclear pore. But how does it get there before the cell is alerted to its presence? Hope and colleagues (McDonald, D. et al. J. Cell Biol., 159, 441–452 (2002)) have visualized the movement of individual HIV particles in live cells and find that in common with other subvertive viruses, HIV does this by 'hitchhiking a ride' with one of the cell's own motors, dynein.
To follow the HIV virions' movement, the authors fused green fluorescent protein (GFP) to one of the viral accessory proteins, Vpr. They then followed the movement of GFP-labelled virions through the cytoplasm of infected cells and showed that they move along a curvilinear path, showing significant association with the microtubule network, but not actin. To address the significance of this association, they looked at the consequences of disrupting the actin or microtubule networks for particle transport. Surprisingly, a complete block in particle transport occurred only when both the actin and microtubule networks were disrupted, suggesting that both are important for HIV movement.
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