Ultrastructural study of heterokaryons from rous rat sarcoma cells and normal chickens cells.

Abstract

Rous virus transformed rat cells containing the Rous virus genome but lacking the ability to produce Rous virus particles have been fused with chicken erythrocytes, chicken lymphocytes or chicken fibroblasts using Sendai virus. Heterokaryotic cells with both rat sarcoma cell nuclei and chicken cell nuclei have been studied in the electron microscope. Shortly after the fusion, a series of changes in the chicken nuclei are demonstrable, which as seen in the electron microscope imply a “reactivation” and production of intranuclear RNA‐containing structures as well as a development of nucleoli. In parallel, the chicken nucleus increases in size and the chromatin is transformed from condensed aggregates into a finely dispersed material. In spite of all evidence of a protein synthesis in the heterokaryotic Rous sarcoma cell directed from the chicken nucleus there is no formation of virus particles in cells with Rous rat sarcoma cells and chicken erythrocytes or chicken lymphocytes. In cultures with Rous rat sarcoma cell—chicken fibroblast heterokaryons a regular synthesis was seen. It seems apparent that the chicken fibroblast contains some factor, whether genetically coded or not, that is required if a production of complete Rous virus particles is to be achieved.