FIG. 11.
Localization of BrUTP as seen by EM. L cells were filled for 2 h with 16-nm gold–BSA that was subsequently chased overnight into late endosomes/lysosomes. The cells were MHV infected, labeled with BrUTP at 4 h p.i., fixed 1 h later, and prepared for cryosectioning. In panels A and B, two rare profiles of BrUTP labeling can be seen. Panel A shows a POL (5-nm gold, small arrows)-positive structure that labels to some extent with anti-BrUTP (10-nm gold, arrowhead), and in panel B, the compartment where the internalized 16-nm gold–BSA (large arrowhead) accumulates is labeled with both CT1a (10-nm gold, arrowheads) and anti-BrUTP (5-nm gold, small arrows). Panels C and D show typical profiles of BrUTP labeling (marked by a large arrow in panel D). Tubular vesicular structures that are attached to the membranes in which the 16-nm gold–BSA accumulates (large arrowheads) are strongly labeled for anti-BrUTP (5-nm gold, small arrows in panel C; 10-nm gold arrowheads in panel D). CT1a in panel C (arrows, 10-nm gold) and POL (small arrows, 5-nm gold) in panel D also label these BrUTP-positive membranes to some extent. N, nucleus. Bars, 100 nm.