Figure 6.

Microinjection of Sar1p^dn to block ER export leads to a slow accumulation by 3 h of gp27 in the ER. HeLa cells were microinjected with Sar1p^dn in the presence of 5 μg/ml emetine to inhibit protein synthesis. Cells were then incubated for 3 h at 37°C in complete media in the presence of emetine. Cells were fixed with formaldehyde and immunofluorescently labeled for gp27. The arrowhead points to the microinjected cell in this example field. Note that a juxtanuclear gp27 staining pattern of noninjected control cells is largely absent in the microinjected cell. Considerable diffuse cytoplasmic fluorescence indicative of ER localization is present in the injected cell. Bar, 10 μm.