what is site-specific integration - (Jan/09/2011 )

Can someone define site-specific integration for me? this would be into the genome. websites or animation describing it would be good too

claritylight on Mon Jan 10 03:05:04 2011 said:

Hola, To me it´s a way to drive the integration of a DNA fragment in an specific site by homologous recombination driven by the ends of the fragment to clone. For instance, one of the methods of obtain recombinant baculovirus is mix a digest DNA wich has beta-gal under the polihedrin promoter; you recombines this DNA with a plasmid wich has complementary sequencies of the sides of beta gal, in the ends of the gene what you want clone, when you transfect the complementary sites annealing and homologous recombination is made, entering your gene into viral DNA and sorting the beta gal gene; in this way the recombinant viruses are distinguish by a white/blue selection with X-galBuena suerte

"Site-specific integration" in regards to DNA refers to integration (insertion) of an extra-chromosomal piece of DNA into the chromosome at a specific recognition site (as opposed to "random integration", where the extra-chromosomal piece can insert anywhere with approximately equal frequency). It is distinct from homologous recombination, in that it is driven by the presence on the chromosome of a particular nucleotide pattern (the site or target) that is recognized by enzymes (site-specific recombinases) that mediate the insertion rather than by long stretches of identity between the chromosome and the extra-chromosomal piece. Integration of viruses and some transposons usually utilize site-specific integration.

See here for an example of the site-specific integration of phage lamda, and here for an overview of site-specific recombination.