Heterochromatin are present along the chromosome (uncoiled state). With the highly-condensed structure relative to euchromatin, RNA polymerase cannot get into the DNA base pairs in heterochromatin and starting transcription.

Question: During DNA replication, heterochromatin are also required to be replicated since they are part of the chromosome. Therefore, I would like to ask whether topoisomerases themselves can unwind this extreme super-coiling or other enzymes / mechanisms are involved in unwinding heterochromatin during DNA replication.

(I have this question in my mind is because I am not sure whether the same unwinding mechanism from topoisomerase can be applied to the super-coiling formed in the already condensed heterochromatin compared to euchromatin) Thank you.


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