The temperature-sensitive defect in polyoma virus P155 mutant

P155 is a temperature-sensitive mutant of polyoma virus that transforms normally, but replicates poorly, under restrictive conditions (Eckhart, 1969, 1975). We have observed that the temperature-sensitive character of P155 maps within the portion of the viral DNA coding exclusively for large T antigen, a viral gene product which is thermolabile in P155-infected cells. The phenotype of P155 may indicate that large T antigen fulfills different functions in virus replications and in cell transformation.