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c-Jun stimulates origin-dependent DNA unwinding by polyomavirus large Tantigen
The EMBO Journal
|October 15, 1996
Summary
The AP1 protein c-Jun significantly enhances polyomavirus DNA replication by aiding the binding of large T antigen (LT) to the origin. This transcription factor interaction is crucial for initiating DNA synthesis.
Area of Science:
- Molecular Biology
- Virology
- Biochemistry
Background:
- The AP1 protein, c-Jun, is known to promote polyomavirus (Py) DNA replication in living organisms.
- The precise mechanism by which c-Jun stimulates Py DNA replication requires further elucidation.
Purpose of the Study:
- To investigate the mechanism by which c-Jun stimulates Py DNA replication in vitro.
- To define the role of c-Jun in the initiation of Py DNA replication.
Main Methods:
- Utilized an in vitro DNA unwinding assay with purified c-Jun and large T antigen (LT).
- Employed mobility shift and DNase I footprinting assays to assess protein-DNA interactions.
- Conducted purified in vitro replication assays to measure DNA synthesis.
Main Results:
- c-Jun stimulated DNA unwinding by approximately 5-fold at limiting LT concentrations.
- Py DNA replication was comparably stimulated by c-Jun in vitro.
- c-Jun enhanced the ATP-dependent binding of LT to the Py origin core by approximately 7-fold.
- c-Jun directly interacts with LT, with stimulatory activity localized to its N-terminal region.
Conclusions:
- c-Jun acts as a co-factor, significantly enhancing LT's ability to bind the Py origin.
- The N-terminal domain of c-Jun plays a key role in stimulating DNA replication initiation.
- Transcription factors may possess replication domains that facilitate the initiation of DNA synthesis.