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Recombinase Enhancer R.C. Johnson and M.F. Bruist. 1989. Intermediates in Hin-mediated DNA inversion: a role for Fis and the recombinational enhancer in the strand exchange reaction [1]

  1. RE sequence must be present
  2. w/o RE, Hin can still assemble to with the two Hix’s however, Hin can’t generate inversion
  3. Prevention of Fis binding causes loss of enhancer function
  4. 60 bp in length
  5. Binds two Fis proteins (98 AA’s)
  6. Enhancer cannot function when located too close to a recombination site
  7. HU facilitates the required bending of the DNA to create the inversion interaction
  8. HU stimulation is dependent upon location of RE
  9. Dependence upon HU is lesser when distance between RE and recombination site is greater
  10. Required to induce the bending of the shorter, yet stiffer, segment of DNA
  11. When RE is located >650 bp for the recombination site the dependence upon HU to form the complex is lost
  12. RE combined w/ supercoiling mediate the rotation of DNA strands subsequent to double-stranded cleavage by Hin within two recombination sites

Haykinson and Johnson. 1993. DNA looping and the helical repeat in vitro and in vivo: effect of HU protein and enhancer location on Hin invertasome assembly [2]

  1. The two recombination sites bound by Hin are assembled together at the Fis-bound RE
  2. w/o HU invertasome assembly is very inefficient
  3. “HU is the only protein in E. coli that can promote invertasome formation with short DNA lengths between RE and recombination sites
  4. HU binds non-specifically to DNA between the enhancer and recombination site to facilitate DNA looping
  5. “The RE can function at great distances !!! >4 kb !!! and on either side of a recombination site on a plasmid to stimulate Hin-mediated DNA inversion”
  6. RE is not functional at a position 32 bp minimum
  7. Due to restricted looping
  8. Enhancer Structure: AGTCAACAATTGACC – 33 bp – GTGCAAATTGTGACC; proximal Fis-binding site of the left and the distal Fis-binding site on the right
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