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Figure 6 | BMC Genomics

Figure 6

From: Divergence of gene regulation through chromosomal rearrangements

Figure 6

Model for the origin of the unique P1-rr 3' end and enhancer region by non-homologous end-joining and unequal crossover. The bottom bar represents the unique P1-rr 3' end with tandem direct repeats. The top bar shows schematically the junction sequence of two P1-wr repeats drawn as tan and grey rectangles. The P1-wr copy at the right side was modified into a P1-rw-like sequence as outlined in Figure 5 (see MULE, filler DNA and repeats depicted as purple, pink and light blue rectangles, respectively). The green rectangle stands for part of a sequence, which was shown to have enhancer function in P1-rr. A model explaining the conversion from a P1-wr and P1-rw1077 sequence to a unique P1-rr structure is briefly described. A DNA double-strand break of unknown cause was expanded by exonuclease activity. DNA repair occurred by non-homologous end-joining as evidenced by filler DNA (yellow rectangle). While the initial 9 bp (ATAATTGGG) of the filler DNA stem from a sequence 55 bp downstream of the deletion end point (see light blue balloon), the adjacent 4 bp TCAC correspond to a sequence 21 bp upstream of the insertion site (tan balloon). The MULE fragment contains an 8-bp sequence TCGATGCC also found 1269 bp further downstream (shown on top of the grey rectangle). Unequal crossover at the 8-bp site resulted in the duplication of the 1269-bp sequence in tandem fashion and addition of a fourth exon.

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