title: DNA compaction in the early part of the SOS response is dependent on RecN and RecA.
abstract: The nucleoids of undamaged Escherichia coli cells have a characteristic shape and number, which is dependent on the growth medium. Upon induction of the SOS response by a low dose of UV irradiation an extensive reorganization of the nucleoids occurred. Two distinct phases were observed by fluorescence microscopy. First, the nucleoids were found to change shape and fuse into compact structures at midcell. The compaction of the nucleoids lasted for 10-20 min and was followed by a phase where the DNA was dispersed throughout the cells. This second phase lasted for ~1 h. The compaction was found to be dependent on the recombination proteins RecA, RecO and RecR as well as the SOS-inducible, SMC (structural maintenance of chromosomes)-like protein RecN. RecN protein is produced in high amounts during the first part of the SOS response. It is possible that the RecN-mediated 'compact DNA' stage at the beginning of the SOS response serves to stabilize damaged DNA prior to recombination and repair.
authors.affiliation: Department of Cell Biology, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway.
authors.forename: Ingvild
authors.initials: I
authors.lastname: Odsbu
authors.affiliation: Department of Cell Biology, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway.
authors.forename: Kirsten
authors.initials: K
authors.lastname: Skarstad
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D004247:DNA / Q000378:metabolism*; D004249:DNA Damage / Q000528:radiation effects; D004262:DNA Restriction Enzymes / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology* / Q000378:metabolism / Q000502:physiology* / Q000528:radiation effects; D008856:Microscopy, Fluorescence; D011938:Rec A Recombinases / Q000378:metabolism*; D013014:SOS Response, Genetics; D013997:Time Factors; D014466:Ultraviolet Rays
chemical_list: D001426:Bacterial Proteins; D004247:DNA; D011938:Rec A Recombinases; D004262:DNA Restriction Enzymes; C047879:RecN protein, Bacteria