Related Experiment Videos
Characterization of polyoma mutants with altered middle and large T-antigens
Abstract:
The viable polyoma mutants dl1013, dl1014, and dl1015 produced shortened middle and large T-antigens. In mouse 3T3 cells, dl1013 and dl1014 grew at normal rates, and dl1015 grew at a reduced rate. dl1015 behaved phenotypically as a double mutant, with deficiencies both in the stimulation of the host cell and the replication of viral DNA. Only the former defect could be complemented by the ts-a mutant, which produced a normal middle T-antigen and a temperature-sensitive large T-antigen. This result suggests that middle T-antigen is involved in the induction of cellular DNA synthesis. Of the three mutants, dl1015 alone failed to transform rat fibroblasts to growth in semisolid medium. This defect could not be complemented by the ts-a mutant. Determination of the base sequences of the mutant DNAs showed that dl1013 and dl1014 had overlapping deletions of 21 and 9 base pairs, respectively, and that the dl1015 deletion of 30 base pairs was contiguous to the other mutations on their 3' sides. Analyses of the mutant t-antigens showed that all three mutants produced shortened middle T-antigens, whereas only dl1015 large T-antigen was detectably reduced in size.
Insights
Polyoma mutants with deletions in T-antigens show impaired host cell stimulation and viral DNA replication. Middle T-antigen is crucial for inducing cellular DNA synthesis, while large T-antigen is essential for transformation.
Area of Science:
- Molecular Biology
- Virology
- Cell Biology
Background:
- Polyoma virus T-antigens play critical roles in viral replication and host cell manipulation.
- Understanding the functions of middle and large T-antigens is essential for deciphering viral pathogenesis and host-pathogen interactions.
Purpose of the Study:
- To investigate the functional consequences of specific deletions in polyoma virus T-antigens.
- To elucidate the roles of middle and large T-antigens in host cell stimulation, viral DNA replication, and cell transformation.
Main Methods:
- Generation and characterization of viable polyoma mutants (dl1013, dl1014, dl1015) with defined deletions in T-antigen genes.
- Growth rate analysis of mutants in mouse 3T3 cells.
- Complementation studies using a ts-a mutant.
- Transformation assays of rat fibroblasts.
- DNA sequencing to confirm deletion sites.
- Analysis of T-antigen protein sizes.
Main Results:
- Mutants dl1013, dl1014, and dl1015 produced shortened middle T-antigens, with dl1015 also showing a reduced large T-antigen.
- dl1015 exhibited defects in host cell stimulation and viral DNA replication, with only the former being complemented by ts-a.
- dl1015 was deficient in transforming rat fibroblasts, a defect not complemented by ts-a.
- Middle T-antigen is implicated in inducing cellular DNA synthesis, while large T-antigen is essential for transformation.
Conclusions:
- Middle T-antigen is essential for the induction of host cell DNA synthesis.
- Large T-antigen is required for the transformation of rat fibroblasts.
- Specific deletions in polyoma T-antigens lead to distinct functional deficits, highlighting the differential roles of middle and large T-antigens.