A new sensitive target-bound DNA binding assay for SV40 large T antigen

Area of Science:

• Molecular Biology
• Virology
• Biochemistry

Background:

• SV40 large T antigen plays a crucial role in viral replication.
• Existing DNA binding assays for large T antigen are often confounded by cellular extract components.
• Standardized analysis of large T antigen DNA binding is needed.

Purpose of the Study:

• To develop a novel, sensitive target-bound DNA binding assay (TB assay) for SV40 large T antigen.
• To overcome limitations of existing assays by using immunopurified large T antigen.
• To enable accurate DNA binding analysis under standardized conditions.

Main Methods:

• Immunopurification of SV40 large T antigen using a specific monoclonal antibody and protein A-Sepharose.
• Incubation of the immune complex with SV40 DNA.
• A two-step elution procedure for separate analysis of bound DNA and large T antigen.
• Determination of equilibrium dissociation constant (Kd).

Main Results:

• The TB assay demonstrated high sensitivity for detecting large T antigen DNA binding.
• Analysis of the SVR9D mutant revealed specific binding to the SV40 ORI, contrary to previous reports.
• The assay allows for the quantification of bound DNA and large T antigen.

Conclusions:

• The developed TB assay provides a sensitive and standardized method for studying SV40 large T antigen DNA binding.
• This assay facilitates the analysis of large T antigen from various sources and mutants.
• The findings challenge previous conclusions regarding SVR9D mutant ORI binding activity.