Bidirectional migration of SeqA-bound hemimethylated DNA clusters and pairing of oriC copies in Escherichia coli.
BACKGROUND
We previously found that SeqA protein, which binds preferentially to newly replicated hemimethylated DNA, is localized as discrete fluorescent foci in Escherichia coli cells. A single SeqA focus, localized at midcell, separates into two foci and these foci migrate abruptly in opposite directions.


RESULTS
The present study shows that (i) appearance of SeqA foci depends on continuous DNA replication, suggesting that the SeqA foci represent clusters consisting of SeqA and newly replicated hemimethylated DNA, (ii) in a synchronous round of replication, a single SeqA focus at midcell separates into two foci and these foci abruptly migrate in opposite directions midway through replication from oriC to the terminus, and (iii) oriC is replicated at midcell but replicated oriC copies remain linked with each other at midcell for 40 min after replication at 30 degrees C. Subsequently, the linked oriC copies separate and migrate gradually towards both borders of the nucleoid before cell division.


CONCLUSIONS
A single cluster of SeqA-bound hemimethylated DNA segment separates into two clusters and these clusters migrate abruptly in a bipolar fashion during progress of replication and prior to separation of linked sister oriC copies.
Hiraga
S
S
Department of Molecular Cell Biology, Institute of Molecular Embryology and Genetics, Kumamoto University School of Medicine, Kumamoto 862-0976, Japan. hiraga@gpo.kumamoto-u.ac.jp
Ichinose
C
C
Onogi
T
T
Niki
H
H
Yamazoe
M
M
D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001692:Biological Transport / Q000235:genetics; D019175:DNA Methylation; D004261:DNA Replication; D004269:DNA, Bacterial / Q000235:genetics* / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics*; D029968:Escherichia coli Proteins; D051738:Origin Recognition Complex; D014157:Transcription Factors; D014764:Viral Proteins / Q000235:genetics
D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C114650:OriC chromosomal replication origin; D051738:Origin Recognition Complex; C089746:SeqA protein, E coli; D014157:Transcription Factors; D014764:Viral Proteins