Question

How is gene expression controlled at the level of the gene or DNA (chromatin level) itself? Give two examples.

Answer 1

The answer is by the process of acetylation and deacetylation. These reactions are catalyzed by histone acetyltransferase (HAT) and histone deacetylase (HDAC) respectively.

If the gene is to be expressed, the HAT initiates the acetylation process attached acetyl groups to histone, it results the lowering of interactions between histone octomers and DNA which results the open or relaxed DNA strcutrues, which is called euchromatin. As the DNA is relaxed form, the RNA pol can move over the DNA and the genes will be pressed.

If the gene is to be regulated or not to be expreesed, then HDAC removes the acetyl groups on the histone proteins, it inceraes the interaction between nucleosomes and DNA. So, the thick condensed form of network will be formed it is called heterochromatin. As a result the RNA pol cannot bind to the DNA, hence the gene expression will be silensed.