Biochemical properties associated with the immortalizing domaine of the large T protein of polyoma virus

Abstract

A fragment of polyoma virus DNA lacking the carboxy-terminal part of the large T antigen coding region is sufficient to express the functions of the entire gene in cell transformation. Two cell lines expressing this truncated DNA were studied, one of them producing a large T-related protein of the expected size (37 kDa) and the other one, a shorter product (34 kDa). Both proteins were phosphorylated and localized in the nucleus, but devoid of ATPase and nucleotide binding activities. As the complete protein, the larger product, but not the shorter variant, exhibited sequence-specific DNA binding properties. These results indicate that ATPase and nucleotide-binding activities are not required for immortalization, and suggest that recognition of specific DNA sequences may be dispensable.