Restricted Infectivity of Ecotropic Type C Retroviruses in Mouse Teratocarcinoma Cells: Studies on Viral DNA Intermediates

摘要

Infectivity of retroviruses in cultured murine teratocarcinoma cells was found to be affected by the state of cellular differentiation. Present studies utilize two kinds of cell cultures from teratocarcinomas of mouse strain 129, an undifferentiated pluriopotential cell line (PCC sub 4 ) and a myoblast-derived cell line (PCD sub 1 ) which are respectively resistant and susceptible to the infection of Gross strain N-tropic type C retrovirus. Analyses of the appearance of free viral DNA intermediates in these cells from 4 to 78 h after virus inoculation were made. In both PCD sub 1 and PCC sub 4 cells, virus inoculation induced the formation of one linear form (III) and two covalently-closed supercoiled circular forms (I) of viral DNA duplexes; the linear form showing its appearance, increase, and decline in the 4 to 18 h period, and the circular forms in the 8 to 24 h period. In the period of 56 to 78 h after virus inoculation, a secondary burst of viral DNA synthesis occurred in PCD sub 1 cells, whereas both linear and supercoiled viral DNA duplexes became undetectable in PCC sub 4 cells. Free and unintegrated viral DNA preparations from PCD sub 1 and PCC sub 4 cells 10 h after virus inoculation were both infectious for N3T3 cells in a DNA transfection assay. Both PCD sub 1 and PCC sub 4 cells were very poor recipients for DNA transfection. These results indicate that restriction of retrovirus in undifferentiated teratocarcinoma cells occurs at a step beyond formation and maturation of viral DNA intermediates. (ERA citation 05:029639)