One of the histone which people are interested at the most is H3.
This is because H3 tail has a huge effect on making euchromatin or heterochromatin.
[H3k4me3]
Let's see its name. "H3" came from histone H3 and "K4" means the position of histone tail of H3 where it is end of tail. Me3 means trimethyl is attached in histone. When H3K4me3 is generated as thrimethyl is attached in H3K4, the nucleosome will be euchromatin to loosely bind DNA and histone. This causes H3K4me3 is located in promoter region a lot, and well known for "transcription activation marker".
[H3k9me2]
H3K9me2 means two of methyl groups are attached to H3 K9 position. This makes heterochromatin, which can cause gene silencing. Let's see more about heterochromatin. In the last posting, we get to know that heterochromatin is region of DNA which tightly tie chromatin. This heterochromatin has two kinds; 1) Constitutive and 2) facultative. Constitive is stable comparable to facultative that is dynamic and fluid. H3K9me3 is known as constitutive heterchomatin marker.
For example, transposable element should be repressed always. In this case, transposable element region should be Constitive heterochromatin rather than facultative. Thus, H3k9me2 is observed in transposable elements in most cases.
[H3k27me3]
H3K27me3 means three of methyl groups are attached to H3 K27 position. H3K27me3 is known as facultative heterchomatin marker.
For example, imprinting genes or genes inducing flowering is repressed by H3k27me3. One of the representative genes regulated by H3k27me3 is FLC gene. FLC is expressed well usually, and then repressed by H3k27me3 in flowering period for bloom.
