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Characterization of a triple DNA polymerase replisome
Peter McInerney1, Aaron Johnson, Francine Katz
1Laboratory of DNA Replication, Howard Hughes Medical Institute, The Rockefeller University, New York, NY 10021, USA.
Molecular Cell
|August 21, 2007
Summary
The bacterial DNA polymerase III holoenzyme contains three DNA polymerases, not two, for DNA replication. This trimeric replicase functions at the replication fork, potentially using the third polymerase as a reserve to overcome obstacles.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- Cellular DNA replication relies on DNA polymerases to synthesize leading and lagging strands.
- DNA polymerases are stabilized on DNA by circular sliding clamps.
Purpose of the Study:
- To investigate the composition and function of the E. coli DNA polymerase III holoenzyme.
- To determine if the replicase contains more than two DNA polymerases and their activity.
Main Methods:
- Analysis of the E. coli DNA polymerase III holoenzyme structure.
- Functional assays at a replication fork.
Main Results:
- The E. coli DNA polymerase III holoenzyme assembles into a particle with three active DNA polymerases.
- This trimeric replicase is functional at the replication fork with other replication machinery.
- It produces slightly shorter Okazaki fragments compared to two-polymerase replisomes.
Conclusions:
- The bacterial replicase likely utilizes three DNA polymerases for DNA synthesis.
- Two polymerases may function on the lagging strand, with the third acting as a reserve enzyme.
- This reserve polymerase could help overcome replication fork obstacles.
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