Replication termination and chromosome dimer resolution in the archaeon Sulfolobus solfataricus

Area of Science:

• Microbiology
• Molecular Biology
• Genetics

Background:

• Archaea, like Sulfolobus, possess single-circular chromosomes with multiple replication origins.
• Replication forks converge and terminate in each cell cycle, raising questions about termination mechanisms.
• Bacterial termination involves specific recombinases (XerC/D), FtsK, and the dif site.

Purpose of the Study:

• To investigate replication termination and dimer resolution in Sulfolobus.
• To determine if Sulfolobus employs similar mechanisms to bacteria for these processes.
• To understand the roles of Xer homologues in Sulfolobus DNA metabolism.

Main Methods:

• Two-dimensional (2D) gel electrophoresis to analyze replication fork fusion zones.
• Gene deletion of the Sulfolobus Xer homologue.
• In vivo and biochemical characterization of Xer/dif recombination.

Main Results:

• Replication termination in Sulfolobus involves stochastic fork collision.
• Deletion of the Xer homologue resulted in aberrant DNA content and cell morphology.
• The chromosomal dif site was identified and characterized, binding Xer in vivo.
• Sulfolobus dif site is located outside replication fork fusion zones.

Conclusions:

• Replication termination and chromosome dimer resolution are temporally and spatially distinct in Sulfolobus.
• Sulfolobus utilizes a unique mechanism for DNA replication termination and dimer resolution compared to bacteria.
• The Xer/dif system in Sulfolobus plays a role in maintaining genome stability but operates independently of replication termination.