Histone Modification
Histone modifications are interpreted to change chromosome function through two different mechanisms. The first claims that these modifications change the electrostatic charge of the histone, resulting in a differentiation of the histones structure on it's bind to DNA. The second claims that these modifications are sites for the binding of protein recognition modules (bromodomains or chromodomains). These modules recognize lysines, acetylated or methylated. (4)
DNA is required to be accessible for DNA-based reactions to occur, such as: replication and repair. DNA is long and nearly endless under the sight of a microscope, but its still has to be compacted into a tiny cell nucleus. This compaction is achieved through histones and their spool like structure that the DNA either winds to tighten or to loosen. Scientists have hypothesized that mechanisms involving histones are what control the accessibility to the DNA, letting in methyl or acethyl residues to the histones. This is thought to also regulate the order and structure of genetic material, plus the recruitment of proteins to the DNA. With this kind of control, histone modification plays a role in epigenetics and it's triggering in the epigenome and an individual's DNA structure. (42)
Post-translational histone modification is a vital mechanism for the regulation of protein function in the DNA. These modifications significantly play in epigenetic memory. There are four key histones: H3, H4, H2A, and H2B. But only two are used to form the nucleosomal particle that DNA wraps itself around. The fifth histone, H1, clings itself to the surface of the nucleosomal particle and causes the stablization of a higher chromatin structure. Histones carry tails, and they are hypothesized to be exposed to several modifications. These modifications are stated to have a "histone code". This "code" is believed to have a modification pattern that is read by proteins, which regulate chromatin and genome functions. Histone modification is established and knkown to be involved in gene regulation that could control complex occurrences such as bodily development or disorders such as cancer. Histone modifying enzymes have been discovered as rearranged, mutated, or deleted in cancer cells. This enhances the comprehension of histone modifications and can significantly impact the identification of new therapeutic targets and diagnostic markers for the treatement of disease and disorders in which epigenetic conditions have become changed or distorted. Currently, these characterized histone modifications are not near complete in research, but deciphering it's function has set a challenged process in biology that shall be furthered for the benefits for the future. (10)