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The Parasite's Way of Life
Published in Eric S. Loker, Bruce V. Hofkin, Parasitology, 2023
Eric S. Loker, Bruce V. Hofkin
As discussed in Chapter 2 (see Figure 2.34) histones are an especially important type of DNA-associated protein found in chromatin. The addition of methyl groups (methylation) to histone proteins is well-known as a mechanism that regulates whether associated DNA is in the heterochromatin or euchromatin form. Methyl groups are added to specific amino acid residues by a group of enzymes called methyltransferases. Histone methylation can either increase or decrease transcription of genes, depending on which amino acids in the histones are methylated and how many methyl groups are added. Methylation events that weaken chemical attractions between histones and DNA increase transcription because they enable the DNA to uncoil, allowing transcription factors and RNA polymerase to access the DNA.
The Role of Epigenetics in Skeletal Muscle Adaptations to Exercise and Exercise Training
Published in Peter M. Tiidus, Rebecca E. K. MacPherson, Paul J. LeBlanc, Andrea R. Josse, The Routledge Handbook on Biochemistry of Exercise, 2020
The heritability of histone modifications and variants has been debated in the literature. Most histone modifications are thought to be highly dynamic, in line with the pulsatile nature of transcriptional responses. Indeed, the half-life of histone acetylation was thought to be 1–2 minutes (26); however, more recent studies suggest that some site-specific acetylation marks have a half-life of up to 30 hours (70). Nonetheless, other histone modifications are more stable, such as methylation, with a half-life of up to a number of days (68). This is sufficient to allow histone-modifying enzymes to replicate modifications from inherited histones to new histones throughout mitotic cell division. Indeed, some histone methyltransferases can recognize and amplify pre-existing histone methylation patterns (32). The influence of epigenetic inheritance on skeletal muscle phenotype will be discussed later in this chapter; however, it is likely that both histone modifications and variants play a role in retaining epigenetic information that influences transcriptional responses.
Epigenetic Alterations in Alzheimer’s Disease and Its Therapeutic and Dietary Interventions
Published in Atanu Bhattacharjee, Akula Ramakrishna, Magisetty Obulesu, Phytomedicine and Alzheimer’s Disease, 2020
P. M. Aswathy, C. M. Shafeeque, Moinak Banerjee
Histone methylation is also dynamic and is carried out by the opposing actions of histone methyltransferases (HMTs) and histone demethylases (HDMTs). Methylation occurs on lysine (mono-, di- or tri-methylated) or arginine residues and does not seem to alter the charge of the altered residues but confers unique structural alterations. Similarly, histone phosphorylation is mediated by the opposing activities of protein kinases and phosphatases. Histone phosphorylation regulates multiple processes, such as DNA damage response, gene expression, chromatin condensation etc.
Epigenetic modulations in cancer: predictive biomarkers and potential targets for overcoming the resistance to topoisomerase I inhibitors
Published in Annals of Medicine, 2023
Moustafa M. Madkour, Wafaa S. Ramadan, Ekram Saleh, Raafat El-Awady
Histone methylation is the dynamic addition of one, two, or three methyl groups to specific amino acids within a histone protein. Nearly all biological processes, including DNA repair, cell cycle, stress response, transcription, development, differentiation, and aging, have been shown to be regulated by histone methylation [109]. Since abnormal histone methylation has been reported to play a causal role in tumorigenesis, it can be linked to anticancer-related drug responses [110]. Histone lysine demethylases (KDMs) are enzymes that catalyze the removal of methyl group from lysine and arginine residues on histone tails and were found to play critical roles in oncogenesis [111]. Addition of the KDM inhibitor 17-DMAG to the clinically tested combination vincristine and irinotecan significantly improved the efficacy of this combination, indicating that targeting KDM may serve as a useful approach for enhancing the response to anticancer drugs like Top I inhibitors [112].
Inhibition of histone demethylase JMJD1C attenuates cardiac hypertrophy and fibrosis induced by angiotensin II
Published in Journal of Receptors and Signal Transduction, 2020
Shenqian Zhang, Ying Lu, Chenyang Jiang
A hallmark of pathological cardiac hypertrophy and fibrosis is the re-expression of fetal genes [2]. Epigenetic modifications are emerging regulators of this transcriptional reprograming [3–5]. Histone methylation is a conserved posttranslational modification, and regulates a multiple of genomic functions, including gene transcription [6]. Di- and tri-methylation of histone 3 lysine 9 (H3K9me2 and H3K9me3) are normally associated with transcriptional repressing and are silenced in hypertrophic and failing hearts in mouse and humans [7–9]. Histone methylation is dynamically controlled by lysine methyltransferases (KMTs) and lysine demethylases (KDMs). Zhang et al. reported that the H3K9me3 demethylase KDM4A/JMJD2A promoted pressure overload-induced LVH associated with activation of fetal genes re-expression [8]. Thienpont et al. reported that the H3K9me2 di-methyltransferase EHMT1/2 protected mice against pressure overload-induced LVH associated with activation of fetal genes re-expression [9]. Zhang et al. reported that the H3K9me2 demethylase KDM3A/JMJD1A promoted pressure overload-induced LVH associated with the activation of fetal genes re-expression [7]. Importantly, besides the H3K9me2/me1 demethylases JMJD1A, JMJD1C was also upregulated and positively associated with heart diseases [7,10,11]. However, its role in pathological heart diseases remains unknown.
Methylation of Specific CpG Sites in IL-1β and IL1R1 Genes is Affected by Hyperglycaemia in Type 2 Diabetic Patients
Published in Immunological Investigations, 2020
Naeimeh Roshanzamir, Vahideh Hassan-Zadeh
T2D is a multifactorial disease in which both genetic and non-genetic factors are involved. Lack of physical activity, obesity, high fat and sugar diet are among non-genetic factors contributing to the development of the disease (Olokoba et al., 2012). Non-genetic factors exert their effect on T2D pathogenesis via epigenetic mechanisms (Pinney and Simmons, 2010). Epigenetics is the study of mitotically and/or meiotically heritable changes in gene expression without changes in the sequence of DNA. Chromatin modifications such as histone acetylation, histone methylation and DNA methylation are well-known epigenetic mechanisms (Armstrong, 2013). In vertebrates, DNA methylation which is catalyzed by DNA methyltransferase enzymes occurs on the 5-carbon position of cytosine bases often in a CpG dinucleotide context. Promoter DNA methylation is usually associated with gene silencing due to the prevention of transcription factor binding or recruitment of methylated DNA binding proteins and their co-repressor protein partners (Armstrong, 2013; Jones, 2012).