Topological locking restrains replication fork reversal.
Two-dimensional agarose gel electrophoresis, psoralen cross-linking, and electron microscopy were used to study the effects of positive supercoiling on fork reversal in isolated replication intermediates of bacterial DNA plasmids. The results obtained demonstrate that the formation of Holliday-like junctions at both forks of a replication bubble creates a topological constraint that prevents further regression of the forks. We propose that this topological locking of replication intermediates provides a biological safety mechanism that protects DNA molecules against extensive fork reversals.
Fierro-Fernández
Marta
M
Centro de Investigaciones Biológicas, Departamento de Biología Celulor, del Desarrollo, Consejo Superior de Investigaciones Cientificas, Ramiro de Maeztu 9, 28040 Madrid, Spain.
Hernández
Pablo
P
Krimer
Dora B
DB
Stasiak
Andrzej
A
Schvartzman
Jorge B
JB
D015139:Blotting, Southern; D003432:Cross-Linking Reagents / Q000494:pharmacology; D004247:DNA / Q000737:chemistry*; D004260:DNA Repair; D004269:DNA, Bacterial / Q000737:chemistry; D004278:DNA, Superhelical / Q000737:chemistry*; D015180:Electrophoresis, Gel, Two-Dimensional / Q000379:methods; D004926:Escherichia coli / Q000378:metabolism; D005363:Ficusin / Q000737:chemistry; D007364:Intercalating Agents / Q000494:pharmacology; D008854:Microscopy, Electron / Q000379:methods; D009690:Nucleic Acid Conformation; D009693:Nucleic Acid Hybridization; D010957:Plasmids / Q000378:metabolism; D013696:Temperature
D003432:Cross-Linking Reagents; D004269:DNA, Bacterial; D004278:DNA, Superhelical; D007364:Intercalating Agents; D004247:DNA; D005363:Ficusin