Temporal progression of PyV nuclear assembly.

<p>Images from dual-axis tomograms of high pressure frozen, Epon-embedded, 300 nm thick sections of 3T3 cells infected with PyV (MOI of 10–20 pfu/cell) and harvested at 32 hpi. <b>A</b>) Tubular structures (black arrowhead) are present in the periphery of the condensed chromatin (Chr) adjacent to occasional virions (white arrowhead). <b>B</b>) A 1 nm section extracted from a 2×2 montage over six serial sections (1.8 µm thick) of a 3T3 nucleus in which the interchromatin space is partially filled with virion clusters and each cluster is associated with tubular structures. As infection proceeds, the number of virus clusters (white arrowhead) increases while the tubular structures (black arrowhead) are less prominent. <b>C</b>) Late in infection virions fill the entire interchromatin space and tubular structures are not seen. <b>D</b>) 3-D model of the 2×2 montage over six serial sections (each 300 nm thick) of a PyV-infected 3T3 nucleus. The model represents 1.8 µm thick section of the nucleus showing the connections between virion clusters and tubular structures. An image extracted from the tomogram is shown in (B); a video of the tomograms of each section and the model can be found as supporting information <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1002630#ppat.1002630.s002" target="_blank">Video S1</a>. Pink spheres, full virions; yellow cylinders, tubular structures. Chr, host condensed chromatin; Cyt, cytoplasm.