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Inhibition of polyoma DNA synthesis by base pair substitutions at the replication origin
Abstract:
The effect of base pair substitutions on the function of the polyoma virus origin of DNA replication was studied. The mutations were all C-G to T-A transitions, induced by bisulfite treatment of recombinant DNA molecules. The mutagenesis was directed to short single-stranded gaps in duplex DNA, or to loops in heteroduplex molecules. Modification of a 34 base pair sequence of dyad symmetry led to cis-acting inhibition of viral DNA synthesis, ranging from slight defects to total inactivation. One of the mutants was temperature sensitive. Mutants with base changes in an adjacent DNA segment, including an 18 base pair long purine-pyrimidine tract, had similar, but less severe, deficiences. In contrast to the effect of mutations in the homologous region of the simian virus 40 genome, there was no strict relationship between mutation of the putative large T-antigen-binding base sequence GPuGGC and defective viral DNA synthesis.
Insights
Altering the polyoma virus origin of DNA replication with specific mutations (C-G to T-A transitions) significantly impacted viral DNA synthesis. Some mutations caused severe defects or inactivation, affecting viral replication efficiency.
Area of Science:
- Molecular Biology
- Virology
- Genetics
Background:
- The polyoma virus origin of DNA replication is crucial for viral propagation.
- Understanding how specific DNA sequences influence replication is key to virology.
Purpose of the Study:
- To investigate the functional impact of base pair substitutions at the polyoma virus origin of DNA replication.
- To identify critical sequences within the origin that regulate viral DNA synthesis.
Main Methods:
- Site-directed mutagenesis using bisulfite treatment to induce C-G to T-A transitions in recombinant DNA.
- Analysis of viral DNA synthesis in cells transfected with mutated DNA molecules.
- Characterization of cis-acting effects on viral DNA replication.
Main Results:
- Modification of a 34 base pair dyad symmetry sequence resulted in cis-acting inhibition of viral DNA synthesis, from minor defects to complete inactivation.
- One mutant exhibited temperature-sensitive replication.
- Mutations in an adjacent 18 base pair purine-pyrimidine tract caused less severe deficiencies.
- Unlike simian virus 40, mutations in the GPuGGC sequence did not strictly correlate with defective viral DNA synthesis.
Conclusions:
- Specific base pair substitutions within the polyoma virus origin of DNA replication significantly affect its function.
- The 34 base pair dyad symmetry region is critical for efficient viral DNA synthesis.
- The relationship between sequence elements and replication function differs between polyoma virus and simian virus 40.