Recombination repair, of DNA

Genetic variation can be increased by an induction of double-stranded breaks in the DNA. The recombination/repair of DNA helix breaks can increase the frequency of nearby base substitutions and frame shifts. For example, V-region hypermutation in the antibody appears to involve the focused generation of DNA breaks at a specific stage in B-cell development. 

Kuzminov, A. (1999). Recombinational repair of DNA damage in Escherichia coli and bacteriophage lambda. Microbiol. Mol. Biol. Rev. 63, 751-813. 

Johnson RD, Liu N, Jasin M. Mammalian XRCC2 promotes the repair of DNA double stranded breaks by homologous recombination. Nature 1999 401 397-399. 

Importantly, the ERCCl/XPF structure-specific nuclease has an additional role in the repair of cisplatin adducts besides its function in NER the recombinational repair of interstrand crosslinks (19). ERCCl- or XPF-deficient hamster mutant cell lines are hypersensitive to DNA crosslink agents, much more so than to ultraviolet-induced pyrimide dimers, the classical substrates for NER (20,21). Moreover, co-localization of ERCCl foci and RAD51 foci in response to cisplatin treatment has recently been found and may represent recruitment of ERCCl/XPF to sites of recombination repair (22). Previous studies have shown that BRCAl, involved in homologous recombination repair, also plays a major role in the repair of cisplatin DNA damage (23). 

Johnson RD, Liu N, Jasin M (1999) Mammalian XRCC2 promotes the repair of DNA double-strand breaks by homologous recombination. Nature 401 397-9 Park MS, Ludwig DL, Stigger E, Lee S-H (1996) Physical interaction between human RAD52 and RPA is required for homologous recombination in mammalian ceUs. J Biol Chem 271 18996-9000... 

Purpose. The purpose of the sister chromatid exchange (SCE) assay is to evaluate the potential of the test substance to induce repair of DNA lesions by homologous recombination in cells of treated animals (potentially all species, usually rodents) (Latt et al. 1981 Helleday 2003). It can easily be applied to any dividing tissue, such as bone marrow and peripheral blood, from which cell suspensions can be isolated and analyzed. 

Araujo, S.J., Tirode, F., Coin, F., Pospiech, H., Syvaoja, J.E., Stucki, M., Hubscher, U., Egly, J.M., and Wood, R.D. (2000) Nucleotide excision repair of DNA with recombinant human proteins definition of the minimal set of factors, active forms of TFIIH, and modulation by CAK. Genes Dev., 14, 349-359. 

Cole, R.S. (1973) Repair of DNA containing interstrand crosslinks in Escherichia coli sequential excision and recombination. Proc. Natl. Acad. Sci. USA, 70, 1064-1068. 

Recombinational Repair - Cellular DNA repair system in which newly replicated DNA duplexes undergo genetic recombination, with ultimate removal of the damaged DNA segment. 

Mitomycin C was found to have broad activity against a range of tumors and has been used clinically since the early 1960s [14, 15]. It causes many specific cellular effects, including inhibition of DNA synthesis, recombination, chromosome breakage, sister chromatid exchange, induction of DNA repair, and induction of... 

Genetic recombination arises by exchange of homologous segments of DNA between viral genomes, most often during the replication process. The enzymes involved in recombination are DNA polymerases, endonucleases, and ligases, which also play a role in DNA repair and synthesis processes. 

DNA ligase is not only important in DNA replication it is also used to seal deoxyri-bonucleotide segments in the crossover events during gene recombination. The enzyme also functions to close breaks in segments of DNA undergoing repair and is required to join theends of mitochondrial DNA to form their characteristic circular structure. 

Most DNA manipulations require the use of purified enzymes. Within cells these enzymes are used for DNA replication and transcription, breakdown of foreign DNA, repair of mutated DNA and recombination between different DNA molecules. Most of the purified enzymes are available commercially. They are usually supplied in Tris buffer containing 50% glycerol and are stored at -20 °C. The glycerol is included in the buffer to prevent freezing but must be removed prior to use as it alters the activity of some enzymes. 

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