The duplication of eukaryotic genomes involves the replication of DNA from multiple origins of replication. In S phase, two sister replisomes assemble at each active origin, and they replicate DNA in opposite directions. Little is known about the functional relationship between sister replisomes. Some data imply that they travel away from one another and thus function independently. Alternatively, sister replisomes may form a stationary, functional unit that draws parental DNA toward itself. If this "double replisome" model is correct, a constrained DNA molecule should not undergo replication. To test this prediction, lambda DNA was stretched and immobilized at both ends within a microfluidic flow cell. Upon exposure to Xenopus egg extracts, this DNA underwent extensive replication by a single pair of diverging replisomes. The data show that there is no obligatory coupling between sister replisomes and, together with other studies, imply that genome duplication involves autonomously functioning replisomes.
Bibliographical noteFunding Information:
We thank Ronald Lebofsky for communicating unpublished results and Charles C. Richardson, Ronald Lebofsky, and Jerard Hurwitz for critical reading of the manuscript. This work was supported by National Institutes of Health (NIH) grant GM62267 and a Leukemia and Lymphoma Scholar Award (to J.C.W.). A.M.v.O. acknowledges support from American Cancer Society grant RSG-08-234-01 and Searle Scholarship 05-L-104. A.B.L. was supported by NIH/NIGMS Molecular Biophysics Training Grant T32 GM008313.
ASJC Scopus subject areas
- Molecular Biology
- Cell Biology