Site-Specific Recombination and Partitioning Systems in the Stable High Copy Propagation of the 2-Micron Yeast Plasmid

摘要

Fig 1 The 2-micron plasmid is a double-stranded circular DNA that is often drawn as a dumbbell to highlight the 599 bp sequence that is repeated in inverted orientation (parallel lines) The open reading frames are schematically represented (FLP, KEPI, KEP2, and RAF1) and their transcriptional orientations are denoted by the arrowheads The target sites for the Flp site-specific recombinase (FRT) are located within the inverted repeats. The DNA sequence and organization of the FRTsite is shown below The Flp protein binds as a monomer to each of the elements la, l'a, and l'b. Only la, l'a, and the included sequence are relevant to the chemical steps of recombination. The vertical arrows denote the phosphodiester bonds that take part in the cleavage and exchange steps. The Rafl protein appears to be a positive regulator of FLP expression The partitioning locus, STB, acts in conjunction with the Repl and Rep2 proteins to mediate efficient plasmid segregation during cell division. The plasmid replication origin is marked as OBI. Flp-mediated recombination is responsible for the existence of the plasmid as an equilibrium mixture of forms A and B.