Immortalization of Mammalian Cells

[0019] The present invention was identified by exploiting a yeast two-hybrid screen to search for cellular proteins that interact with the amino terminus of SV40 T antigen. It was shown that T antigen interacts specifically with the mitotic spindle assembly checkpoint protein, Bub1 (Hoyt et al., 1991). This interaction was confirmed by reciprocal co-immunoprecipitation analysis in a wide variety of cell types. Genetic analysis indicated that a specific tryptophan-containing motif on T antigen is required for its interaction with Bub1. Interaction with Bub1 is not required for immortalisation by T antigen but is necessary for transformation. T antigen expression results in a partial disruption of the spindle assembly checkpoint such that cells can undergo mitosis even in the presence of low levels of spindle damage. T antigen mutants that fail to interact with Bub1are defective in their ability to modulate the spindle checkpoint.

[0020] The binding site for Bub1 on T antigen is distinct