Histone H3
Encyclopedia
Histone H3 is one of the five main histone
protein
s involved in the structure of chromatin
in eukaryotic cell
s. Featuring a main globular domain and a long N-terminal tail
, H3 is involved with the structure of the nucleosome
s of the 'beads on a string' structure. Histone proteins are highly post-translationally modified however Histone H3 is the most extensively modified of the five histones. The term "Histone H3" alone is purposely ambiguous in that it does not distinguish between sequence variants or modification state. Histone H3 is an important protein in the emerging field of epigenetics
, where its sequence variants and variable modification states are thought to play a role in the dynamic and long term regulation of genes.
core and can undergo several different types of post-translational modification that influence cellular processes. These modifications include the covalent attachment of methyl or acetyl groups to lysine
and arginine
amino acids and the phosphorylation of serine
or threonine
. Di- and Tri-methylation of Lysine 9 are associated with repression and heterochromatin, while mono-methylation of K9 is associated with active genes. has been associated with gene silencing
and the formation of relatively inactive regions of DNA known as heterochromatin
. Acetylation of histone H3 occurs at several different lysine positions in the histone tail and is performed by a family of enzymes known as histone acetyltransferase
s (HATs). Acetylation of lysine14 is commonly seen in genes that are being actively transcribed into RNA
.
H1
H2A
H2B
H4
Histone
In biology, histones are highly alkaline proteins found in eukaryotic cell nuclei that package and order the DNA into structural units called nucleosomes. They are the chief protein components of chromatin, acting as spools around which DNA winds, and play a role in gene regulation...
protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
s involved in the structure of chromatin
Chromatin
Chromatin is the combination of DNA and proteins that make up the contents of the nucleus of a cell. The primary functions of chromatin are; to package DNA into a smaller volume to fit in the cell, to strengthen the DNA to allow mitosis and meiosis and prevent DNA damage, and to control gene...
in eukaryotic cell
Eukaryotic Cell
Eukaryotic Cell is an academic journal published by the American Society for Microbiology. The title is commonly abbreviated EC and the ISSN is 1535-9778 for the print version, and 1535-9786 for the electronic version....
s. Featuring a main globular domain and a long N-terminal tail
N-terminal end
The N-terminus refers to the start of a protein or polypeptide terminated by an amino acid with a free amine group . The convention for writing peptide sequences is to put the N-terminus on the left and write the sequence from N- to C-terminus...
, H3 is involved with the structure of the nucleosome
Nucleosome
Nucleosomes are the basic unit of DNA packaging in eukaryotes, consisting of a segment of DNA wound around a histone protein core. This structure is often compared to thread wrapped around a spool....
s of the 'beads on a string' structure. Histone proteins are highly post-translationally modified however Histone H3 is the most extensively modified of the five histones. The term "Histone H3" alone is purposely ambiguous in that it does not distinguish between sequence variants or modification state. Histone H3 is an important protein in the emerging field of epigenetics
Epigenetics
In biology, and specifically genetics, epigenetics is the study of heritable changes in gene expression or cellular phenotype caused by mechanisms other than changes in the underlying DNA sequence – hence the name epi- -genetics...
, where its sequence variants and variable modification states are thought to play a role in the dynamic and long term regulation of genes.
Epigenetics and Post-Translational Modifications
The N-terminal tail of histone H3 protrudes from the globular nucleosomeNucleosome
Nucleosomes are the basic unit of DNA packaging in eukaryotes, consisting of a segment of DNA wound around a histone protein core. This structure is often compared to thread wrapped around a spool....
core and can undergo several different types of post-translational modification that influence cellular processes. These modifications include the covalent attachment of methyl or acetyl groups to lysine
Lysine
Lysine is an α-amino acid with the chemical formula HO2CCH4NH2. It is an essential amino acid, which means that the human body cannot synthesize it. Its codons are AAA and AAG....
and arginine
Arginine
Arginine is an α-amino acid. The L-form is one of the 20 most common natural amino acids. At the level of molecular genetics, in the structure of the messenger ribonucleic acid mRNA, CGU, CGC, CGA, CGG, AGA, and AGG, are the triplets of nucleotide bases or codons that codify for arginine during...
amino acids and the phosphorylation of serine
Serine
Serine is an amino acid with the formula HO2CCHCH2OH. It is one of the proteinogenic amino acids. By virtue of the hydroxyl group, serine is classified as a polar amino acid.-Occurrence and biosynthesis:...
or threonine
Threonine
Threonine is an α-amino acid with the chemical formula HO2CCHCHCH3. Its codons are ACU, ACA, ACC, and ACG. This essential amino acid is classified as polar...
. Di- and Tri-methylation of Lysine 9 are associated with repression and heterochromatin, while mono-methylation of K9 is associated with active genes. has been associated with gene silencing
Gene silencing
Gene silencing is a general term describing epigenetic processes of gene regulation. The term gene silencing is generally used to describe the "switching off" of a gene by a mechanism other than genetic modification...
and the formation of relatively inactive regions of DNA known as heterochromatin
Heterochromatin
Heterochromatin is a tightly packed form of DNA, which comes in different varieties. These varieties lie on a continuum between the two extremes of constitutive and facultative heterochromatin...
. Acetylation of histone H3 occurs at several different lysine positions in the histone tail and is performed by a family of enzymes known as histone acetyltransferase
Histone acetyltransferase
Histone acetyltransferases are enzymes that acetylate conserved lysine amino acids on histone proteins by transferring an acetyl group from acetyl CoA to form ε-N-acetyl lysine....
s (HATs). Acetylation of lysine14 is commonly seen in genes that are being actively transcribed into RNA
RNA
Ribonucleic acid , or RNA, is one of the three major macromolecules that are essential for all known forms of life....
.
Sequence Variants
Mammalian cells have three known sequence variants of histone H3. These are denoted as Histone H3.1, Histone H3.2 and Histone H3.3 but are highly sequence conserved differing only by a few amino acids.Genetics
Histone H3s are coded by several genes in the human genome, including:- H3.1: HIST1H3AHIST1H3AHistone H3.1 is a protein that in humans is encoded by the HIST1H3A gene.-Further reading:...
, HIST1H3BHIST1H3BHistone H3.1 is a protein that in humans is encoded by the HIST1H3B gene.-Further reading:...
, HIST1H3CHIST1H3CHistone H3.1 is a protein that in humans is encoded by the HIST1H3C gene.-Further reading:...
, HIST1H3DHIST1H3DHistone H3.1 is a protein that in humans is encoded by the HIST1H3D gene.-Further reading:...
, HIST1H3EHIST1H3EHistone H3.1 is a protein that in humans is encoded by the HIST1H3E gene.-Further reading:...
, HIST1H3FHIST1H3FHistone H3.1 is a protein that in humans is encoded by the HIST1H3F gene.-Further reading:...
, HIST1H3GHIST1H3GHistone H3.1 is a protein that in humans is encoded by the HIST1H3G gene.-Further reading:...
, HIST1H3HHIST1H3HHistone H3.1 is a protein that in humans is encoded by the HIST1H3H gene.-Further reading:...
, HIST1H3IHIST1H3IHistone H3.1 is a protein that in humans is encoded by the HIST1H3I gene.-Further reading:...
, HIST1H3JHIST1H3JHistone H3.1 is a protein that in humans is encoded by the HIST1H3J gene.-Further reading:... - H3.2: HIST2H3A, HIST2H3CHIST2H3CHistone H3.2 is a protein that in humans is encoded by the HIST2H3C gene.-Further reading:...
, HIST2H3D - H3.3: H3F3AH3F3AHistone H3.3 is a protein that in humans is encoded by the H3F3A gene.-Further reading:...
, H3F3B
See also
- Other histoneHistoneIn biology, histones are highly alkaline proteins found in eukaryotic cell nuclei that package and order the DNA into structural units called nucleosomes. They are the chief protein components of chromatin, acting as spools around which DNA winds, and play a role in gene regulation...
proteins:
H1
Histone H1
Histone H1 is one of the five main histone protein families which are components of chromatin in eukaryotic cells. Though highly conserved, it is nevertheless the most variable histone in sequence across species.- Structure :...
H2A
Histone H2A
Histone H2A is one of the 5 main histone proteins involved in the structure of chromatin in eukaryotic cells. Featuring a main globular domain and a long N terminal tail, H2A is involved with the structure of the nucleosomes of the 'beads on a string' structure.Other histone proteins...
H2B
Histone H2B
Histone H2B is one of the 5 main histone proteins involved in the structure of chromatin in eukaryotic cells. Featuring a main globular domain and a long N terminal tail H2B is involved with the structure of the nucleosomes of the 'beads on a string' structure.See nucleosome, histone and...
H4
Histone H4
Histone H4 is one of the 5 main histone proteins involved in the structure of chromatin in eukaryotic cells. Featuring a main globular domain and a long N terminal tail, H4 is a structural component of the nucleosome, and is subject to covalent modification, including acetylation and methylation,...
- NucleosomeNucleosomeNucleosomes are the basic unit of DNA packaging in eukaryotes, consisting of a segment of DNA wound around a histone protein core. This structure is often compared to thread wrapped around a spool....
- HistoneHistoneIn biology, histones are highly alkaline proteins found in eukaryotic cell nuclei that package and order the DNA into structural units called nucleosomes. They are the chief protein components of chromatin, acting as spools around which DNA winds, and play a role in gene regulation...
- ChromatinChromatinChromatin is the combination of DNA and proteins that make up the contents of the nucleus of a cell. The primary functions of chromatin are; to package DNA into a smaller volume to fit in the cell, to strengthen the DNA to allow mitosis and meiosis and prevent DNA damage, and to control gene...