A DOMAIN OF MURINE RETROVIRUS SURFACE PROTEIN GP70 MEDIATES CELL-FUSION, AS SHOWN IN A NOVEL SC-1 CELL-FUSION SYSTEM

Virus-induced cell fusion of the fusion-from-without type was observed in SC-1 cells infected with Moloney murine leukemia virus when grown in NIH 3T3 cells. Replication-competent virus mutants with altered sur face protein gp70 were examined. Fusion mutations were found in the pr oline-rich region of gp70. They acted on a step after binding and befo re or during endocytosis. The fusion mutants had an altered gp70 isome r pattern, presumably caused by different glycosylation. Other mutants with deleted glycans were analyzed, add some which also showed defect ive fusion were found. The interrelationship of the proline-rich regio n, glycosylation, and fusion is discussed.