DNA recombinases are widely used in multicellular organisms to manipulate the structure of
genomes, and to control
gene expression. These enzymes, derived from
bacteria (
bacteriophages) and
fungi, catalyze directionally sensitive DNA exchange reactions between short (30–40
nucleotides) target
site sequences that are specific to each recombinase. These reactions enable four basic functional modules: excision/insertion, inversion, translocation and
cassette exchange, which have been used individually or combined in a wide range of configurations to control gene expression.[1][2][3][4][5]
The archaeon Sulfolobus solfataricus RadA recombinase catalyzes
DNA pairing and strand exchange, central steps in recombinational repair.[6] The RadA recombinase has greater similarity to the eukaryotic
Rad51 recombinase than to the bacterial RecA recombinase.[6]
Bacteria
RecA recombinase appears to be universally present in bacteria. RecA has multiple functions, all related to
DNA repair. RecA has a central role in the repair of replication forks stalled by
DNA damage and in the bacterial sexual process of natural
genetic transformation.[7][8]
Eukaryotes
Eukaryotic
Rad51 and its related family members are homologous to the archaeal RadA and bacterial RecA recombinases. Rad51 is highly conserved from yeast to humans. It has a key function in the recombinational repair of DNA damages, particularly double-strand damages such as double-strand breaks. In humans, over- or under-
expression of Rad51 occurs in a wide variety of
cancers.
During
meiosis Rad51 interacts with another recombinase,
Dmc1, to form a presynaptic filament that is an intermediate in
homologous recombination.[9] Dmc1 function appears to be limited to meiotic recombination. Like Rad51, Dmc1 is homologous to bacterial RecA.
Viruses
Some DNA viruses encode a recombinase that facilitates homologous recombination. A well-studied example is the UvsX recombinase encoded by
bacteriophage T4.[10] UvsX is homologous to bacterial RecA. UvsX, like RecA, can facilitate the assimilation of linear single-stranded DNA into an homologous DNA duplex to produce a
D-loop.
^Michod RE, Bernstein H, Nedelcu AM (2008). "Adaptive value of sex in microbial pathogens". Infect. Genet. Evol. 8 (3): 267–85.
doi:
10.1016/j.meegid.2008.01.002.
PMID18295550.
^Bernstein C, Bernstein H (2001). DNA repair in bacteriophage. In: Nickoloff JA, Hoekstra MF (Eds.) DNA Damage and Repair, Vol.3. Advances from Phage to Humans. Humana Press, Totowa, NJ, pp. 1–19.
ISBN978-0896038035