Question

2. Speculate all the different kinds of interaction of histones with DNA in the nucleosome that may contribute to its structural stability. Where on the nucleosome do you think this interaction maybe the weakest? In this context also discuss what is meant by the “histone fold”?

Answer 1

Chromatin is a double stranded helical structure of DNA. DNA is complexed with histone proteins to form nucleosomes in order to attain stability. Each nucleosome consist of eight histone proteins around which 147 basepairs of DNA wraps 1.65 times. Each 8 histone proteins nucleosome core is linked with the DNA strand through H1 histone protein known as linker H1 protein. A combination of nucleosome with H1 histone is known as chromatosome. The nucleosomes fold up to form a 30 nm chromatin fiber which forms loops averaging 300 nanometers in length. The 300 nm fibers are compressed and folded to produce a 250 nm-wide fiber, which is tightly coiled into the chromatid of a chromosome.

The position of the nucleosome opposite to the H1 linker nucleosome core has wekest interaction as H1 histone tighly joins the DNA strand with histone protein.