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#site-specific recombination

2 public questions tagged with this topic.

Recombination

Cre-loxP system is an example of

Bacteriophage P1 encodes Cre recombinase to circularize linear genome after infection and maintain plasmid prophage state. Cre functions on 34 base-pair loxP sites without assisting factors or DNA synthesis, performing reciprocal exchange through tyrosine-mediated transient DNA-protein covalent intermediate. Because recombination occurs between defined sites irrespective of homology length or cellular recombination machinery, it exemplifies tyrosine family site-specific recombination. Laboratory exploitation of Cre-loxP enables conditional gene deletion, insertion, and inversion in eukaryotic genomes, demonstrating autonomous site-specific system, distinct from homologous recombination, non-homologous end joining, or transposition pathways requiring transposase.

Ref: Lodish et al., Molecular Cell Biology, 9th ed., Chapter 8: Cre-loxP as Tyrosine Site-Specific Recombination System

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Recombination

Site-specific recombination does NOT require

Homologous recombination depends on extensive sequence homology, dozens to hundreds of base pairs, and requires RecA/Rad51 mediated homology search. Site-specific recombination operates by entirely different logic. It uses specialized recombinases recognizing short 20-200 base-pair asymmetric attachment sites such as loxP, attP/attB, or FRT, assembling synaptic tetramers that perform concerted strand cleavage, exchange, and ligation without need for long homology, DNA synthesis, or RecA. Reaction specificity relies on DNA bending proteins like IHF, and outcome depends solely on relative orientation of sites enabling excision, inversion, or integration.

Ref: Alberts et al., Molecular Biology of the Cell, 7th ed., Chapter 5: Site-Specific Recombination Mechanism Differences

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