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- Title
Organization of DNA in a bacterial nucleoid.
- Authors
Tolstorukov, Michael Y.; Virnik, Konstantin; Zhurkin, Victor B.; Adhya, Sankar
- Abstract
Background: It is unclear how DNA is packaged in a bacterial cell in the absence of nucleosomes. To investigate the initial level of DNA condensation in bacterial nucleoid we used in vivo DNA digestion coupled with high-throughput sequencing of the digestion-resistant fragments. To this end, we transformed E. coli cells with a plasmid expressing micrococcal nuclease. The nuclease expression was under the control of AraC repressor, which enabled us to perform an inducible digestion of bacterial nucleoid inside a living cell. Results: Analysis of the genomic localization of the digestion-resistant fragments revealed their non-random distribution. The patterns observed in the distribution of the sequenced fragments indicate the presence of short DNA segments protected from the enzyme digestion, possibly because of interaction with DNA-binding proteins. The average length of such digestion-resistant segments is about 50 bp and the characteristic repeat in their distribution is about 90 bp. The gene starts are depleted of the digestion-resistant fragments, suggesting that these genomic regions are more exposed than genomic sequences on average. Sequence analysis of the digestion-resistant segments showed that while the GC-content of such sequences is close to the genome-wide value, they are depleted of A-tracts as compared to the bulk genomic DNA or to the randomized sequence of the same nucleotide composition. Conclusions: Our results suggest that DNA is packaged in the bacterial nucleoid in a non-random way that facilitates interaction of the DNA binding factors with regulatory regions of the genome.
- Subjects
BACTERIAL nucleoids; DNA condensation; DNA-binding proteins; NUCLEASES; NUCLEOTIDE sequencing
- Publication
BMC Microbiology, 2016, Vol 16, p1
- ISSN
1471-2180
- Publication type
Article
- DOI
10.1186/s12866-016-0637-3