Some viruses acquire their envelopes by budding through internal membranes of their host cell. We have expressed the cloned cDNA for glycoproteins from two such viruses, the E l protein of coronavirus, which buds in the Golgi region, and VPlO protein of rotavirus, which assembles in the endoplasmic reticulum. Messenger RNA was prepared from both cDNAs by using SP6 polymerase and either translated in vitro or injected into cultured CVl cells or Xenopus oocytes. In CVl cells, the E l protein was localised to the Golgi region and VPlO protein to the endoplasmic reticulum. In Xenopus oocytes, the E l protein acquired post-translational modifications indistinguishable from the sialylated, O-linked sugars found on viral protein, while the VPlO protein acquired endoglycosidase-H-sensitive Nlinked sugars, consistent with their localisation to the Golgi complex and endoplasmic reticulum, respectively. Thus the two proteins provide models with which to study targeting to each of these intracellular compartments. When the RNAs were expressed in matured, meiotic oocytes, the VPlO protein was modified as before, but the E l protein was processed to a much lesser extent than in interphase oocytes, consistent with a cessation of vesicular transport during cell division.