Methylation strongly enhances DNA bending in the replication origin region of the Escherichia coli chromosome.
Two-dimensional gel electrophoresis, at high and low temperatures, and gel mobilities of circularly permuted DNA segments showed a large bending locus about 50 bp downstream from the right border of the 245 bp oriC box, a minimal essential region of autonomous replication on the Escherichia coli chromosome. Bending was strongly enhanced by Dam methylation. In DNA from a Dam- strain, the mobility anomaly arising from altered conformation was much reduced, but was raised to the original level by methylation in vivo or in vitro. Enhancement of the mobility anomaly was also observed by hybrid formation of the Dam- strand with the Dam+ strand. Near the bending center, GATC, the target of Dam methylase, occurs seven times arranged essentially on the same face of the helix with 10.5 bp per turn. We concluded that small bends at each Dam site added up to the large bending detectable by gel electrophoresis.
Kimura
T
T
Institute for Chemical Research, Kyoto University, Japan.
Asai
T
T
Imai
M
M
Takanami
M
M
D001426:Bacterial Proteins / Q000235:genetics; D001483:Base Sequence; D002876:Chromosomes, Bacterial; D004261:DNA Replication; D004269:DNA, Bacterial / Q000378:metabolism*; D015180:Electrophoresis, Gel, Two-Dimensional; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism; D029968:Escherichia coli Proteins; D008745:Methylation; D008780:Methyltransferases / Q000378:metabolism; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D015183:Restriction Mapping; D015265:Site-Specific DNA-Methyltransferase (Adenine-Specific); D013696:Temperature
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D008780:Methyltransferases; C058693:Dam methyltransferase; D015265:Site-Specific DNA-Methyltransferase (Adenine-Specific); C499294:dam protein, E coli