The role of chromatin-associated protein Hbsu in beta-mediated DNA recombination is to facilitate the joining of distant recombination sites.
The beta recombinase is unable to mediate in vitro DNA recombination between two directly oriented recombination sites unless a bacterial chromatin-associated protein (Bacillus subtilis Hbsu or Escherichia [correction of Eschrichia] coli HU] is provided. By electron microscopy, we show that the role of Hbsu is to help in joining the recombination sites to form a stable synaptic complex. Some evidence supports the fact that Hbsu works by recognizing and stabilizing a DNA structure at the recombination site, rather than by serving as a bridge between beta recombinase dimers through a protein-protein interaction. We show that the mammalian HMG1 protein, which shares neither sequence nor structural homology with Hbsu, can also stimulate beta-mediated recombination. These chromatin-associated proteins share the property of binding to DNA in a relatively non-specific fashion, bending it, and having a marked preference for altered DNA structures. Hbsu, HU or HMG1 proteins probably bind specifically at the crossing-over region, since at limiting protein-DNA molar ratios they could not be outcompeted by an excess of a DNA lacking the crossing over site. Distamycin, a minor groove binder that induces local distortions in DNA, did not affect the binding of beta protein to DNA, but inhibited the formation of the synaptic complex.
Alonso
J C
JC
Centro Nacional de Biotecnología, C.S.I.C., Campus Universidad Autónoma de Madrid, Spain.
Gutierrez
C
C
Rojo
F
F
D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology*; D004254:DNA Nucleotidyltransferases / Q000235:genetics / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology*; D004214:Distamycins / Q000494:pharmacology; D006609:High Mobility Group Proteins / Q000502:physiology*; D019426:Integrases; D015394:Molecular Structure; D010957:Plasmids; D045522:Recombinases; D011995:Recombination, Genetic
D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D004214:Distamycins; C075779:Hbsu protein, bacteria; D006609:High Mobility Group Proteins; D045522:Recombinases; C040330:histone-like protein HU, bacteria; C030000:stallimycin; D004254:DNA Nucleotidyltransferases; D019426:Integrases; C115006:integron integrase IntI1