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EZH2, as a part of PRC2, catalyzes trimethylation of H3K27 (), which is a histone modification that has been characterized as part of the histone code.[16] [20] [21] [22] The histone code is the theory that chemical modifications, such as methylation, acetylation, and ubiquitination, of histone proteins play distinctive roles in epigenetic regulation of gene transcription.
Methylation of histones can either increase or decrease transcription of genes, depending on which amino acids in the histones are methylated, and how many methyl groups are attached. Methylation events that weaken chemical attractions between histone tails and DNA increase transcription because they enable the DNA to uncoil from nucleosomes so ...
In addition to processes that regulate transcription at the stage of initiation, mRNA synthesis is also controlled by the rate of transcription elongation. [10] RNA polymerase pauses occur frequently and are regulated by transcription factors, such as NusG and NusA, transcription-translation coupling , and mRNA secondary structure.
These DNA methyltransferases can also methylate CpG sites within the coding regions of genes, where such methylation can increase gene transcription. [34] Work with DNMT3a1 showed it preferentially localized to CpG islands bivalently marked by H3K4me3 (a transcription promoting mark) and H3K27me3 (a transcription repressive mark), coinciding ...
The cis position induces compact histones and decreases the ability of proteins to bind to the DNA, thus preventing methylation of K36 and decreasing gene transcription. Conversely, the trans position of P38 promotes a more open histone conformation, allowing for K36 methylation and leading to an increase gene transcription. [36]
This is because adenine introduced into the new DNA strand is unmethylated. Re-methylation occurs within two to four seconds, during which time replication errors in the new strand are repaired. Methylation, or its absence, is the marker that allows the repair apparatus of the cell to differentiate between the template and nascent strands.
Methylation, as well as other epigenetic modifications, affects transcription, gene stability, and parental imprinting. [2] It directly impacts chromatin structure and can modulate gene transcription, or even completely silence or activate genes, without mutation to the gene itself. Though the mechanisms of this genetic control are complex ...
The mechanism of action of transcription coregulators is to modify chromatin structure and thereby make the associated DNA more or less accessible to transcription. In humans several dozen to several hundred coregulators are known, depending on the level of confidence with which the characterisation of a protein as a coregulator can be made. [ 2 ]