Figure 10

Electron microscopic analysis of 293T cells cotransfected with pNL4-3Luc(R-E-) and pTracer-Emp ( a , and inset a' ) or pTracer-EED ( b-f ) at 3 μg each plasmid per 2 × 10⁶ cell sample, and harvested at 48 h posttransfection. (a), Control cells without exogenous EED expression. Note the number of viral particles budding at the cell surface. Inset (a'), Enlargement of one virus particle at an intermediate step of budding and egress. (b), EED3/4-expressing cells showing very rare budding events at the plasma membrane. Several clusters of ringlike structures (arrows) were observed in the cytoplasm, at distance from the nuclear envelope. Their dimensions (70–80 nm in overall diameter) and constitutive elements (electron-dense annular granules of 15–18 nm in diameter and central channel of 25–27 nm) were characteristic of nuclear pore complexes. (c-f), Enlargement of cytoplasmic areas from EED3/4-expressing cells showing clusters of nuclear pores (NP), viewed in tangential (c) or transversal (d, e) section, and in association with filaments arranged in bundles (F). (f), Cytoplasmic area of EED3/4-expressing cell showing intracytoplasmic vesicles at higher magnification. Note the local thickening of the vesicular membrane and the intraluminal budding of virus-like particles. N, nucleus ; C, cytoplasm ; M, mitochondria.