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DNA Recombination:- Complete Chromosome Replication Can Require Site-Specific Recombination

المؤلف:  David L. Nelson، Michael M. Cox

المصدر:  Lehninger Principles of Biochemistry

الجزء والصفحة:  988

2026-07-22

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DNA Recombination:- Complete Chromosome Replication Can Require Site-Specific Recombination

Recombinational DNA repair of a circular bacterial chromosome, while essential, sometimes generates deleterious byproducts. The resolution of a Holliday junction at a replication fork by a nuclease such as RuvC, followed by completion of replication, can give rise to one of two products: the usual two monomeric chromosomes or a contiguous dimeric chromosome (Fig. 1). In the latter case, the covalently linked chromosomes cannot be segregated to daughter cells at cell division and the di viding cells become “stuck.” A specialized site-specific recombination system in E. coli, the XerCD system, con verts the dimeric chromosomes to monomeric chromo somes so that cell division can proceed. The reaction is a site-specific deletion reaction. This is another example of the close coordination between DNA recombination processes and other aspects of DNA metabolism.

FIGURE 1 DNA deletion to undo a deleterious effect of re combinational DNA repair. The resolution of a Holliday intermediate during recombinational DNA repair (if cut at the points indicated by red arrows) can generate a contiguous dimeric chromosome. A specialized site-specific recombinase in E. coli, XerCD, converts the dimer to monomers, allowing chromosome segregation and cell division to proceed.