An SV40 mutant oncoprotein has a nuclear location.

Area of Science:

• Molecular Biology
• Virology
• Cell Biology

Background:

• Simian virus 40 (SV40) large T antigen is crucial for viral replication and cellular transformation.
• The precise domains responsible for SV40 T antigen's transforming activity remain incompletely understood.
• Previous studies suggest both nuclear and plasma membrane localization of wild-type T antigen in transformed cells.

Purpose of the Study:

• To investigate the role of the N-terminal region of SV40 large T antigen in cellular transformation.
• To determine the minimal transforming domain of SV40 T antigen.
• To compare the cellular localization of a truncated T antigen mutant with wild-type T antigen.

Main Methods:

• Generation of a double SV40 mutant (T147) lacking small t antigen and encoding a truncated large T antigen (147 amino acids).
• Focus assay using C3H10T1/2 mouse cells to assess transformation.
• Agar suspension assay using F111 rat cells to evaluate anchorage-independent growth.
• Immunofluorescence microscopy to determine the subcellular localization of the mutant T antigen.

Main Results:

• The T147 double mutant SV40 successfully transformed C3H10T1/2 mouse cells and F111 rat cells.
• These findings demonstrate that the transforming domain of SV40 T antigen resides within its N-terminal 147 amino acids.
• T147 mutant T antigen localized to the nucleus, similar to wild-type T antigen, but was not detected in the plasma membrane.

Conclusions:

• The N-terminal 147 amino acids of SV40 T antigen are sufficient for cellular transformation.
• Plasma membrane localization of SV40 T antigen is not essential for transformation.
• The study refines our understanding of the structure-function relationship of SV40 T antigen domains.