Topological challenges to DN Conformations at the fork

Le résumé fourni par la source

The unwinding of the parental DNA duplex during replication AI causes a positive linking number difference, or superhelical a strain, to build up around the elongating replication fork. The nc branching at the fork and this strain bring about different wr conformations from that of (-) supercoiled DNA that is not so being replicated. The replicating DNA can form (+) precatus enanes, in which the daughter DNAs are intertwined, and (+) re] supercoils. Topoisomerases have the essential role of relieving Al the superhelical strain by removing these structures. Stalled ca replication forks of molecules with a (+) superhelical strain have pa the additional option of regressing, forming a four-way junction re at the replication fork. This four-way junction can be acted on by re recombination enzymes to restart replication. Replication and chromosome folding are made easier by topological domain th barriers, which sequester the substrates for topoisomerases into in; defined and concentrated regions. Domain barriers also allow di: replicated DNA to be (-) supercoiled. We discuss the importance nc of replicating DNA conformations and the roles of topoisomerth ases, focusing on recent work from our laboratory. to D]

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