Epigenetic marks

In contrast to simple charge neutralization effects, the effects on protein recog-nition/recruitment are collectively referred to as the histone code . This hypothesis predicts that specific patterns of histone tail acetylations and other modifications serve as epigenetic marks for distinct sets of regulatory proteins to differentially modulate chromatin structure and function (Strahl and Allis, 2000 Turner, 2000 Jenuwein and Allis, 2001). Indeed, several recent findings have demonstrated that histone acetylation creates a signal for the binding of a bromodomain which has... 

Figure 3. Schematic representation of the interplay of the various epigenetic marks and its therapeutic potential DNA methylation causes the concomitant deacetylation of the histones, whereby it negatively (—) coixelates with histone acetylation and positively (+) with histone methylation, particularly the repressive marks. The active methylation marks correlate positively with histone acetylation. The loss of activity or the loss or mistargeting of these activities are the most common cause of epigenetic diseases. Shown in the boxes are the small molecular modulators (a, activators or i, inhibitors) of the various enzymes that have potential to develop epigenetic therapeutics...

In mammals the histones are removed and replaced by transition basic proteins in mid-spermatids and then the transition basic proteins are replaced by protamines in late spermitids and sperm [119]. In mouse and rat sperm, histones removal is complete or nearly so [119,120], but in humans 15% of the DNA remains associated with histones [121]. In bovine sperm more than 99% of the histones are removed, but CENP-A is quantitatively retained [122]. This retained CENP-A could be part of an epigenetic mark that allows the positions of the centromeres to be retained in sperm and on the paternal chromosomes of the zygote. 

First, it should be noted that most of the modules whose structures were determined so far often represent subdomains of epigenetic effectors. Indeed, a landmark of many of these proteins is to be composed of different modules, some responsible for epigenetic marks recognition and others bearing catalytic activities. 

Thus, SirT2 is a major contributor to the inheritance of epigenetic marks through mitosis (21). 

Delgado-Calle J, Garmilla P, Riancho JA (2012) Do epigenetic marks govern bone mass and homeostasis Curr Genomics 13 252-263... 

Boron nucleic acid bases, nucleosides and nucleotides 12MR0418. Chemical synthesis of nucleoside analogues 13MI19. 5-Hydroxymethylcytosine The elusive epigenetic mark in mammalian DNA 12CSR6916. 

To date, at least five biotinylation sites have been identified in histones H3 [lysine (K)-4, K9, K18 and probably K23] and H4 (K8, K12 and probably K16) (Camporeale et al. 2004 Kobza et al. 2005 Kobza et al. 2008). K9 and K13 in histone H2A might also be biotinylated (Chew et al. 2006), but the abundance of these two marks appears to be very low (Stanley et al. 2001). Studies with synthetic HLCS substrates provide unambiguous evidence that biotinylation of histones by HLCS is a substrate-specific process (Hassan et al. 2009a). Histone biotinylation is a comparably rare event (<0.1% of histones are biotinylated), but the abundance of an epigenetic mark is not necessarily a marker for its importance. For example, serine-14 phosphorylation in histone H2B and histone poly(ADP-ribosylation) are detectable only after induction of apoptosis... 

Epigenetics An epigenetic trait is a stably inherited phenotype resulting from changes in a chromosome without alterations in the DNA sequence. Epigenetic marks include cytosine (hydroxy)methylation and various histone modifications. 

Hydroxymethylcytosine (5-hmc), an oxidized form of 5-methylcytosine (5-mc), is an epigenetic mark discovered recently in certain mammalian tissues [77, 78]. The function of 5-hmC in epigenetic regulation is thought to be different... 

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