AI Article Synopsis
- - The study discusses how the structure of DNA changes during replication and when proteins are removed in lab conditions, and highlights the impact of superhelical stress on the DNA during this process.
- - Topo IV, an enzyme, plays a crucial role in relaxing supercoiled DNA ahead of replication forks, but it isn't the only player; DNA gyrase also helps in this process, suggesting a teamwork approach in vivo.
- - Even though Topo IV isn't as effective at unlinking certain DNA structures after replication, its main function seems to be managing the linked DNA strands, which is why replication can still happen without it, but the sister DNA strands remain entangled.
Article Abstract
The topology of DNA duplexes changes during replication and also after deproteinization in vitro. Here we describe these changes and then discuss for the first time how the distribution of superhelical stress affects the DNA topology of replication intermediates, taking into account the progression of replication forks. The high processivity of Topo IV to relax the left-handed (+) supercoiling that transiently accumulates ahead of the forks is not essential, since DNA gyrase and swiveling of the forks cooperate with Topo IV to accomplish this task in vivo. We conclude that despite Topo IV has a lower processivity to unlink the right-handed (+) crossings of pre-catenanes and fully replicated catenanes, this is indeed its main role in vivo. This would explain why in the absence of Topo IV replication goes-on, but fully replicated sister duplexes remain heavily catenated.
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