Cre recombinase
Encyclopedia
Cre recombinase, often abbreviated to Cre, is a Type I topoisomerase
from P1 bacteriophage
that catalyzes site-specific recombination of DNA between loxP sites. The enzyme does not require any energy cofactors and Cre-mediated recombination
quickly reaches equilibrium between substrate and reaction products. The loxP recognition element is a 34 base pair (bp) sequence composed of two 13 bp inverted repeats flanking an 8 bp spacer region which confers directionality. Recombination products are dependent on the location and relative orientation of the loxP sites. Two DNA species containing single loxP sites will be fused whilst DNA between loxP sites in the same orientation will be excised in circular form and DNA between opposing loxP sites will be inverted with respect to the rest of the DNA.http://www.neb.com/nebecomm/products/productM0298.asp
Cre recombinase is used as a tool to modify genes and chromosomes. In this approach the Cre recombinase is used to delete a segment of DNA flanked by LoxP sites (aka 'floxed') in an experimental animal. It has been used to generate animals with mutations limited to certain cell types (tissue-specific knockout) or animals with mutations that can be activated by drug administration (inducible knockout) in a number of transgenic species. The availability of transgenic lines with tissue specific or inducible Cre expression permits researchers to inactivate or activate a gene of interest simply by breeding a floxed animal to pre-existing Cre-transgenics. One example of an inducible Cre recombinase system is the Cre-ER (ER = Estrogen Receptor
) system in which intraperitoneal injection
of tamoxifen
will cause dose-dependent
excision of the floxed site (i.e. will inactivate the gene of choice).
Topoisomerase
Topoisomerases are enzymes that regulate the overwinding or underwinding of DNA. The winding problem of DNA arises due to the intertwined nature of its double helical structure. For example, during DNA replication, DNA becomes overwound ahead of a replication fork...
from P1 bacteriophage
Bacteriophage
A bacteriophage is any one of a number of viruses that infect bacteria. They do this by injecting genetic material, which they carry enclosed in an outer protein capsid...
that catalyzes site-specific recombination of DNA between loxP sites. The enzyme does not require any energy cofactors and Cre-mediated recombination
Cre-Lox recombination
Cre-Lox recombination is a special type of site-specific recombination developed by Dr. Brian Sauer initially for use in activating gene expression in mammalian cell lines and transgenic mice . Subsequently, the laboratory of Dr...
quickly reaches equilibrium between substrate and reaction products. The loxP recognition element is a 34 base pair (bp) sequence composed of two 13 bp inverted repeats flanking an 8 bp spacer region which confers directionality. Recombination products are dependent on the location and relative orientation of the loxP sites. Two DNA species containing single loxP sites will be fused whilst DNA between loxP sites in the same orientation will be excised in circular form and DNA between opposing loxP sites will be inverted with respect to the rest of the DNA.http://www.neb.com/nebecomm/products/productM0298.asp
Cre recombinase is used as a tool to modify genes and chromosomes. In this approach the Cre recombinase is used to delete a segment of DNA flanked by LoxP sites (aka 'floxed') in an experimental animal. It has been used to generate animals with mutations limited to certain cell types (tissue-specific knockout) or animals with mutations that can be activated by drug administration (inducible knockout) in a number of transgenic species. The availability of transgenic lines with tissue specific or inducible Cre expression permits researchers to inactivate or activate a gene of interest simply by breeding a floxed animal to pre-existing Cre-transgenics. One example of an inducible Cre recombinase system is the Cre-ER (ER = Estrogen Receptor
Estrogen receptor
Estrogen receptor refers to a group of receptors that are activated by the hormone 17β-estradiol . Two types of estrogen receptor exist: ER, which is a member of the nuclear hormone family of intracellular receptors, and the estrogen G protein-coupled receptor GPR30 , which is a G protein-coupled...
) system in which intraperitoneal injection
Intraperitoneal injection
Intraperitoneal injection or IP injection is the injection of a substance into the peritoneum . IP injection is more often applied to animals than humans...
of tamoxifen
Tamoxifen
Tamoxifen is an antagonist of the estrogen receptor in breast tissue via its active metabolite, hydroxytamoxifen. In other tissues such as the endometrium, it behaves as an agonist, hence tamoxifen may be characterized as a mixed agonist/antagonist...
will cause dose-dependent
Dose-response relationship
The dose-response relationship, or exposure-response relationship, describes the change in effect on an organism caused by differing levels of exposure to a stressor after a certain exposure time...
excision of the floxed site (i.e. will inactivate the gene of choice).