engleski

Homologous recombination in Escherichia coli: A model for the formation of invasive DNA strands

A model for the formation of invasive (recombinogenic) DNA strands during homologous recombination in wild-type Escherichia coli is presented. (a) The 'recombination machine' binds linear duplex DNA. In addition to the RecBCD enzyme, RecS, the product(s) of the recS locus (identitfied in our laboratory) can be regarded as a part of this machine. (b) The RecBCDS complex begins to unwind and degrade DNA. The 5' ended chain is initially spared from degradation. This chain is potentially invasive but RecS prevents its participation in recombination. (c) The recombination machine continues to travel through duplex DNA. It eventually encounters the recombinational hot spot Chi (5'GCTGGTGG 3'). In some way, Chi stimulates incision of the 5' terminal strand and dissociaton of the RecD-RecS complex from the recombination machine. The RecBCD nuclease-helicase is converted into the RecBC helicase (recombinase). (d) The RecBC enzyme then unwinds DNA, releasing single strands of both 5'and 3' polarities. These strands are recombinogenic and they have the ability to substitute for each other in conjugational and transductional recombination. It is assumed that only the undamaged strand (irrespective of the polarity) can participate in recombinational repair.

Genetic recombination; Escherichia coli; recB gene; recC gene; recD gene; recS locus

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