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. 2014 Sep 4;33(21):2507–2520. doi: 10.15252/embj.201488398

Figure 1. Replication of the BU-1 locus.

Figure 1

  1. Cartoon of the domain structure of the Bu-1 protein, adapted from UniProt (http://www.uniprot.org) protein ID Q90746 (Tregaskes et al, 1996).
  2. The predicted impact of the −3 and +3.5 G4 motifs on replication of the BU-1 locus (ENSGALG00000015461). The exons are coloured to reflect their contribution to the domain structure of the protein as shown in (A). In the upper panel, the +3.5 G4 motif has formed a G quadruplex structure, which has stalled the leading strand polymerase resulting in the formation of a post-replicative gap. This results in a zone in which histone recycling is interrupted and therefore in which the histone modifications characteristic of the parental chromatin are lost, in this case H3K4me3 and H3K9/14ac. In the lower panel, a fork approaching from the 5′ end encounters a G quadruplex structure formed by the −3 G4 motif on the lagging strand template. This does not result in formation of a long post-replicative gap or in any perturbation to histone recycling and mark propagation around the TSS of BU-1.
  3. The BU-1 locus is at the centre of an early replicating domain. S-phase cells were BrdU pulse-labelled, sorted into two fractions (Early-S and Late-S). BrdU-DNA from early and late fractions was differentially labelled and cohybridised to a chicken whole-genome microarray at a density of one probe every 5.6 kb. The log2 ratios (Early/Late) of the abundance were smoothed and are shown for two independent experiments. The timing analysis reveals that the BU-1 locus replicates early in S phase but lies between two regions replicated just a little earlier. The markers −3 to +3 indicate the qPCR primers used to validate the array data (Supplementary Fig S1 and Supplementary Table S1).