ppat-1000701-g002: Electron microscopic evidence of direct virion tethering and virion-incorporation of BST-2.HeLa cells were transfected to express the complete HIV-1 genome (wild type; A, C, and E) or a genome lacking vpu (Δvpu; B, D, F, and G), then stained for cell surface BST-2 and processed for electron microscopy as described in the legend of Figure 1. Panels A-F are images of thin sections obtained using a JEOL 1200C microscope operated at 80 keV. Panel G is a projection view of a thick section (approximately 250 nm) derived from a tomographic tilt series of images obtained using an FEI Titan electron microscope operated at 300 keV.