cell lines established in vitro from tumors induced by polyoma virions , polyoma virus dna i , or polyoma virus dna that had been cleaved with restriction endonucleases in the early region all contain the polyoma virus middle and small t antigens but not the large t antigen of polyoma virus is not required for maintenance of the transformed state and probably not for initiation of tumorigenesis by viral dna .
C1510411
transformed
C0007621
tumorigenesis