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The T/t common region of simian virus 40 large T antigen contains a distinct transformation-governing sequence

E Marsilio1, S H Cheng, B Schaffhausen

  • 1Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts 02115.

Journal of Virology
|October 1, 1991
PubMed

Insights

Simian virus 40 large T antigen's (T) transforming ability is linked to its amino-terminal 82 residues. This region contains specific sequences governing T's transforming function and stability, independent of pRb/p107 binding.

Area of Science:

  • Virology
  • Molecular Biology
  • Cellular Transformation

Background:

  • Simian virus 40 large T antigen (T) is known to transform cultured cells, but its precise functional mechanisms remain unclear.
  • Prior research suggests the N-terminal 130 residues of T may be sufficient for cellular transformation.
  • The N-terminal region of T shares homology with simian virus 40 small t antigen (t).

Purpose of the Study:

  • To investigate the role of the amino-terminal residues of Simian virus 40 large T antigen (T) in cellular transformation.
  • To identify specific regions within the N-terminus responsible for T's transforming activity and protein stability.
  • To elucidate the mechanism by which the N-terminal region contributes to T's function, particularly concerning pRb and p107 interactions.

Main Methods:

  • Oligonucleotide-directed mutagenesis was employed to create deletion and substitution mutants.
  • Mutants were generated within the amino-terminal 82 residues of the T antigen.
  • Stability and transformation assays were performed on the generated mutants.

Main Results:

  • The 1-to-82 region of T contains critical sequences that regulate its transforming activity.
  • This N-terminal region also influences the in vivo stability of the T antigen.
  • Genetic analysis demonstrated that instability and impaired transforming activity could be independently attributed to specific mutations within this region.
  • The identified segment contributes to T's transforming function through mechanisms distinct from pRb and/or p107 binding.

Conclusions:

  • The amino-terminal 82 residues of Simian virus 40 large T antigen (T) are crucial for its transforming capability.
  • A specific sub-region within the 1-to-82 segment dictates T's transforming function and affects its stability.
  • The transforming mechanism mediated by this N-terminal region does not rely on the direct binding of pRb or p107 proteins.

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