H3K4me3
H3K4me3
Main page

H3K4me3

logo
Community Hub0 subscribers
What are your thoughts?
Be the first to start a discussion here.
Be the first to start a discussion here.
H3K4me3

H3K4me3 is an epigenetic modification to the DNA packaging protein Histone H3 that indicates tri-methylation at the 4th lysine residue of the histone H3 protein and is often involved in the regulation of gene expression. The name denotes the addition of three methyl groups (trimethylation) to the lysine 4 on the histone H3 protein.

H3 is used to package DNA in eukaryotic cells (including human cells), and modifications to the histone alter the accessibility of genes for transcription. H3K4me3 is commonly associated with the activation of transcription of nearby genes. H3K4 trimethylation regulates gene expression through chromatin remodeling by the NURF complex. This makes the DNA in the chromatin more accessible for transcription factors, allowing the genes to be transcribed and expressed in the cell. More specifically, H3K4me3 is found to positively regulate transcription by bringing histone acetylases and nucleosome remodelling enzymes (NURF). H3K4me3 also plays an important role in the genetic regulation of stem cell potency and lineage. This is because this histone modification is found more in areas of the DNA that are associated with development and establishing cell identity.

H3K4me3 indicates trimethylation of lysine 4 on histone H3 protein subunit:

This diagram shows the progressive methylation of a lysine residue. The tri-methylation (right) denotes the methylation present in H3K4me3.

The H3K4me3 modification is created by a lysine-specific histone methyltransferase (HMT) transferring three methyl groups to histone H3. H3K4me3 is methylated by methyltransferase complexes containing a protein WDR5, which contains the WD40 repeat protein motif. WDR5 associates specifically with dimethylated H3K4 and allows further methylation by methyltransferases, allowing for the creation and readout of the H3K4me3 modification. WDR5 activity has been shown to be required for developmental genes, like the Hox genes, that are regulated by histone methylation.

H3K4me3 is a commonly used histone modification. H3K4me3 is one of the least abundant histone modifications; however, it is highly enriched at active promoters near transcription start sites (TSS) and positively correlated with transcription. H3K4me3 is used as a histone code or histone mark in epigenetic studies (usually identified through chromatin immunoprecipitation) to identify active gene promoters.

H3K4me3 promotes gene activation through the action of the NURF complex, a protein complex that acts through the PHD finger protein motif to remodel chromatin. This makes the DNA in the chromatin accessible for transcription factors, allowing the genes to be transcribed and expressed in the cell.

The genomic DNA of eukaryotic cells is wrapped around special protein molecules known as histones. The complexes formed by the looping of the DNA are known as chromatin. The basic structural unit of chromatin is the nucleosome: this consists of the core octamer of histones (H2A, H2B, H3 and H4) as well as a linker histone and about 180 base pairs of DNA. These core histones are rich in lysine and arginine residues. The carboxyl (C) terminal end of these histones contribute to histone-histone interactions, as well as histone-DNA interactions. The amino (N) terminal charged tails are the site of the post-translational modifications, such as the one seen in H3K4me1.

See all
User Avatar
No comments yet.