Figure 7From: Structural analysis of hemicatenated DNA loopsModel for the mechanism of formation of hcDNA. The central poly(CA) and poly(TG) sequences of the DNA fragment are represented in blue and red, the terminal non-repetitive sequences are in green. After denaturation, reassociation of the strands of the DNA fragment can occur either without a shift, thus reforming the initial fragment in its regular linear conformation, or with a shift, resulting in an intermediate in which the CA and TG strands are only paired on part of their length, leaving a stretch of single-stranded poly(CA) on one side and an equal and complementary length of single-stranded poly(TG) on the other side (arrows), plus the single-stranded non-repetitive sequences at both ends (A). In the presence of HMGB1, this intermediate can fold and form a loop when one of the single-stranded repetitive sequences inserts in the fork formed by the two single strands at the opposite end and pairs with the complementary single-stranded repetitive sequence (B). The hemicatenane thus formed is then stabilized after reassociation of the non-repetitive regions at both ends of the fragment (C) and rearrangement of the structure to maximize base pairing (D).Back to article page