The MRX complex is a heterotrimeric

protein complex A protein complex or multiprotein complex is a group of two or more associated polypeptide chains. Protein complexes are distinct from multienzyme complexes, in which multiple catalytic domains are found in a single polypeptide chain. Protein ...

consisting of

Mre11 Double-strand break repair protein MRE11 is an enzyme that in humans is encoded by the ''MRE11'' gene. The gene has been designated ''MRE11A'' to distinguish it from the pseudogene ''MRE11B'' that is nowadays named ''MRE11P1''. Function This ge ...

Rad50 DNA repair protein RAD50, also known as RAD50, is a protein that in humans is encoded by the ''RAD50'' gene. Function The protein encoded by this gene is highly similar to ''Saccharomyces cerevisiae'' Rad50, a protein involved in DNA double- ...

, and Xrs2. It is a budding yeast homolog of the mammalian Mre11-Rad50-Nbs1 (MRN) DNA damage repair complex.

Double-strand break repair

Cells are able to accurately repair DNA double-strand breaks using a process called

homologous recombination Homologous recombination is a type of genetic recombination in which genetic information is exchanged between two similar or identical molecules of double-stranded or single-stranded nucleic acids (usually DNA as in cellular organisms but may ...

. By this process DNA sequence information that is lost because of the breakage can be recovered from a second homologous DNA molecule. Homologous recombinational repair is important for removing DNA damage both during mitosis and

meiosis Meiosis (; , since it is a reductional division) is a special type of cell division of germ cells in sexually-reproducing organisms that produces the gametes, such as sperm or egg cells. It involves two rounds of division that ultimately r ...

. The repair process begins with the degradation of the 5’ end on either side of the double-strand break to yield 3’ single-stranded DNA tails (a process called end resection). Next the Rad51 protein binds to these tails and initiates a process of strand invasion leading to recovery of genetic information from the undamaged homologous sequence of the second DNA molecule. Studies with the yeast ''

Saccharomyces cerevisiae ''Saccharomyces cerevisiae'' () (brewer's yeast or baker's yeast) is a species of yeast (single-celled fungus microorganisms). The species has been instrumental in winemaking, baking, and brewing since ancient times. It is believed to have b ...

'' have shown that end resection is catalyzed by the MRX protein complex. The

MRE11 Double-strand break repair protein MRE11 is an enzyme that in humans is encoded by the ''MRE11'' gene. The gene has been designated ''MRE11A'' to distinguish it from the pseudogene ''MRE11B'' that is nowadays named ''MRE11P1''. Function This ge ...

enzyme (one of the three component proteins of the MRX complex) first makes a nick in the DNA at 15 to 20 nucleotides from the 5’ end of the break. This creates an entry point for further processing by exonucleases to complete the initial resection stage of the overall process.

References

Protein complexes {{protein-stub