| Summary: | In prokaryotes the genome is organized in a dynamic
structure called the nucleoid, which is embedded in
the cytoplasm. We show here that in the archaeon
Haloferax volcanii, compaction and reorganization of
the nucleoid is induced by stresses that damage the
genome or interfere with its replication. The fraction
of cells exhibiting nucleoid compaction was proportional
to the dose of the DNA damaging agent, and
results obtained in cells defective for nucleotide excision
repair suggest that breakage of DNA strands
triggers reorganization of the nucleoid. We observed
that compaction depends on the Mre11-Rad50
complex, suggesting a link to DNA double-strand
break repair. However, compaction was observed in a
radA mutant, indicating that the role of Mre11-Rad50
in nucleoid reorganisation is independent of homologous
recombination. We therefore propose that
nucleoid compaction is part of a DNA damage
response that accelerates cell recovery by helping
DNA repair proteins to locate their targets, and facilitating
the search for intact DNA sequences during
homologous recombination.
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