The rubella virus E1 glycoprotein is arrested in a novel post-ER, pre- Golgi compartment

That the site of E1 arrest is not a dead end and presumably lies along the main route of exocytic traffic, was demonstrated by the finding that VSV G protein synthesized by the ts045 mutant which is defective in ER to Golgi transport at 39.5~ could enter the tubular network at the restrictive teanperature, and then exit this compartment when shifted to the permissive temperature. Taken together, the collective findings suggest that the site of E1 arrest corresponds to, or is located in close proximity to the exit site from the ER system which is highly amplified under these conditions, i.e., overexpression of unassembled E1 subunits. It appears that E1 subunits travel to the extreme distal extensions of the ER where they can go no further in the absence of E2, accumulate, and are degraded with a half-life of 6 h.