Question

The physical association between the histone octamer and DNA can be disrupted in numerous ways.What are they?

Answer 1

Different types of chemical modifications of histone proteins and DNA molecules are involved in disrupting the physical association between the histone octamer and DNA. Some of the ways to disrupt histone-DNA interaction are -

i) Acetylation of histone tails (acetyl groups added to lysine) in nucleosome core particles reduces the affinity of the histones for DNA binding.

ii) Methylation of histone tails at lysine and arginine at certain positions (H3K4, H3K36) are associated with disrupting histone-DNA association by binding of some proteins, and thus activates transcription.

iii) Chromatin remodelling complexes break the bond between histone octamer and DNA, they require energy from ATP to do this. They may replace the histone octamer by sliding or remove the histone completely.

iv) H2A-H2B dimer displacement or exchange by some histone chaperone proteins.

v) Acidic proteins or treatment with acidic solutions can displace basic histones from the DNA.