Fig. 2. The ER network in the budding yeast S. cerevisiae. Wild-type yeast cells expressing the ER membrane protein Sec63p fused to GFP were visualized by epifluorescence microscopy. The left panel reveals the appearance of cortical ER tubules and the nuclear envelope in the center of a large-budded cell. Cytoplasmic ER tubules that connect cortical ER and the nuclear envelope are readily seen at this focal plane. Focusing on the periphery of the cell (right panel) allows the visualization of the cortical network of interconnected tubules. Figure reproduced with permission from The Rockefeller University Press (Prinz et al., 2000). Both cortical ER and the nuclear envelope remain intact during mitosis.