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J. Cell Biol.,
Volume 144, Number 4, February 22, 1999 657-672
Institute of Zoology, University of Zürich, CH-8057 Zürich, Switzerland
Adenovirus (Ad) enters target cells by receptor-mediated endocytosis, escapes to the cytosol,
and then delivers its DNA genome into the nucleus.
Here we analyzed the trafficking of fluorophore-tagged viruses in HeLa and TC7 cells by time-lapse microscopy. Our results show that native or taxol-stabilized
microtubules (MTs) support alternating minus- and
plus end-directed movements of cytosolic virus with elementary speeds up to 2.6 µm/s. No directed movement was observed in nocodazole-treated cells. Switching between plus- and minus end-directed elementary speeds
at frequencies up to 1 Hz was observed in the periphery
and near the MT organizing center (MTOC) after recovery from nocodazole treatment. MT-dependent motilities allowed virus accumulation near the MTOC at
population speeds of 1-10 µm/min, depending on the
cell type. Overexpression of p50/dynamitin, which is
known to affect dynein-dependent minus end-directed
vesicular transport, significantly reduced the extent and
the frequency of minus end-directed migration of cytosolic virus, and increased the frequency, but not the extent of plus end-directed motility. The data imply that a
single cytosolic Ad particle engages with two types
of MT-dependent motor activities, the minus end-
directed cytoplasmic dynein and an unknown plus end-
directed activity.
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