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

The absence of o~-mannosidase II together with the ultrastructural findings suggested that E1 was arrested in a smooth membrane compartment that did not correspond to the Golgi complex. To determine whether any E1 entered the Golgi complex immunoprecipitates from radiolabeled CHOE1 cells were digested with endo H. Consistent with previous work (20) , only a small fraction of E1 entered the Golgi as evidenced by the time-dependent appearance of an endo H-resistant form (Fig. 4, arrowhead) ; most of the E1 (>80%) remained endo H-sensitive throughout the chase period, indicating that the bulk of the glycoprotein did not reach the middle Golgi complex. Beyond 2-h chase periods, significant turnover of E1 was observed (see below), rendering it difficult to accurately determine how much of the protein had reached the Golgi complex.