Homologous Recombination in Mammalian Cells

Development of a positive–negative selection procedure for gene targeting in fish cells

“…Cultured mammalian somatic cells are quite proficient at randomly integrating transfected DNA (Waldman et al, 1996), and the frequency of homologous recombination in non-ES cells is typically several orders of magnitude lower than in ES cells (Bollag et al, 1989). The observation that PCR screening failed to detect unambiguous homologous recombination events in more than 100 G418 r -Gc r colonies led to the inference that these colonies might contain randomly integrated homologous recombination vectors, in which the tk gene cassette was destroyed by exonuclease degradation.…”

Theoretical mechanisms in targeted and random integration of transgene DNA

“…The reported ratio of random to targeted integration varies enormously, from around 1:4 to more than 1000000:1. In most cases, the ratio is between 1 000:1 and 10 000:1 [4,8,13,35,43,46]. It is noteworthy that the low efficiency of targeted integration in mammalian cells is in marked contrast to that which occurs when DNA is transfected into lower eukaryotes such as yeast: under appropriate empirical conditions, targeting is the norm and random integration the exception for such organisms.…”

Mutant p53 proteins stimulate spontaneous and radiation-induced intrachromosomal homologous recombination independently of the alteration of the transactivation activity and of the G1 checkpoint

“…Homologous recombination is an essential mechanism involved in fundamental processes such as DNA repair (Friedberg et al, 1995), molecular evolution (Liebhaber et al, 1981;Arnheim, 1983), gene diversi®cation (Baltimore, 1981;Reynaud et al, 1987;Becker and Knight, 1990) and chromosome segregation during meiosis (Roeder, 1990;Kleckner, 1996). Contrasting with its role in genome maintenance, homologous recombination between homologous sequences dispersed through the genome, may lead to profound rearrangements such as: inversions, deletions, duplications (Bollag et al, 1989). Additionally, gene conversion leads to loss of heterozygosity when acting between two heteroalleles (Cavenee et al, 1983;Xia et al, 1994) or to gene inactivation when acting between a gene and a related pseudogene (Amor et al, 1988).…”