SeqA is responsible for delayed separation at late-splitting loci.

(A) Loss of SeqA reduces cohesion at snaps and oriC, but not at non-snap loci dnaB and arcA. WT and ΔseqA strains bearing tetO arrays at each of the five loci shown were grown in minimal alanine media and assayed for cohesion as described in Figure 1 (3 independent experiments ±1 SD). (B) Representative micrographs of wildtype and ΔseqA cells showing nucleoids (DAPI) and gln TetR-YFP foci. ΔseqA cells exhibit ∼2% anucleate cells (arrow). (C) E. coli chromosome map with cohesion-characterized loci [6]. Snap loci (red) and oriC (green) have prolonged cohesion periods (19–30 min); non-snap loci (blue) have short cohesion periods (7–10 min). (D) Sites with prolonged cohesion bind more SeqA. SeqA binding levels at 5 loci shown were determined by ChIP-qPCR. Relative binding (2−ΔΔCt) indicates SeqA binding relative to the poorest binding sequence, dnaB. (E) Genomic analysis of GATC frequency, SeqA binding, and cohesion. GATC per kb (top panel), and SeqA binding from two SeqA ChIP-chip studies; Waldminghaus et. al. [31] (middle panel) and Sanchez-Romero et. al. [32] (lower panel), 40-kb moving average of SeqA binding is shown (log2 ratio of IP to input fluorescence). Positions of cohesion-characterized loci are shown as colored vertical lines.