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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.
Genetics and exercise: an introduction
Published in Adam P. Sharples, James P. Morton, Henning Wackerhage, Molecular Exercise Physiology, 2022
Claude Bouchard, Henning Wackerhage
How does the CH3 methyl group become added to some cytosines and what is the consequence? Cytosines are methylated by enzymes, called DNA methyltransferases. The resultant cytosine methylation then typically reduces gene transcription. This is because methylation reduces transcription factor binding to that region of DNA. Because CpG sites and CpG islands are located more frequently around promoter regions, reduced transcription factor binding after increased methylation suppresses gene transcription. In contrast, reduced methylation (demethylation or hypomethylation) of CpG sites in a promoter region can increase gene transcription, by allowing transcription factor binding. Exceptions are if increased methylation occurs in a silencer or repressor element where it can therefore increase transcription. CpG islands can be methylated (or demethylated) in the basal, natural state, but cytosine residues also become more or less methylated in response to nutrients, environmental stressors, exercise and other stimuli.
Overview of Perinatal Maternal Stress
Published in Rosa Maria Quatraro, Pietro Grussu, Handbook of Perinatal Clinical Psychology, 2020
Dawn Kingston, Muhammad Kashif Mughal
DNA methylation occurs with the addition of a methyl group to the DNA molecule (Constantinof et al., 2016). The methyl group suppresses gene expression by preventing transcription factors from binding so that the DNA is less available for transcription (Kundakovic & Jaric, 2017). With respect to prenatal stress, most DNA methylation occurs in genes within the HPA-related glucocorticoid pathway (Cao-Lei et al., 2017).
Targeted sequencing approach: Comprehensive analysis of DNA methylation and gene expression across blood and brain regions in suicide victims
Published in The World Journal of Biological Psychiatry, 2023
Katarina Kouter, Tomaž Zupanc, Alja Videtič Paska
DNA methylation is the addition of a single methyl group to a cytosine, leading to formation of 5-methylcytosine (5mC) (Prokhortchouk and Defossez 2008). The reaction is catalysed by enzymes from the DNA methyltransferases (DNMT) family, with the donor of methyl group being S-adenosyl methionine (Lyko 2018). 5mC can usually be found clustered in CpG dinucleotide motifs. CpG clusters form CpG islands (CGI) and act as regulators of gene expression in promoters and first exons (Deaton and Bird 2011). Methylation of a promotor CpG island is often associated with decreased levels of gene expression (Illingworth and Bird 2009). DNA methylation may affect gene expression following two mechanisms. First, addition of a methyl group alters DNA biophysical properties and prevents the binding of transcriptional factors to DNA (Lee et al. 2014). Second, it attracts proteins that bind to methylated DNA and thus prevent gene transcription (Du et al. 2015).
Epigenetic regulation by gut microbiota
Published in Gut Microbes, 2022
Vivienne Woo, Theresa Alenghat
DNA methylation is an epigenetic modification whereby methyl groups (-CH3) are covalently added to cytosine or adenine bases by DNA methyltransferases (DNMTs) using the donor metabolite SAM. Methylated DNA residues are often located within CpG Islands and are generally associated with gene repression by physically restricting access of regulatory mediators to the DNA, especially when located near gene promoters. Changes in DNA methylation were initial evidence that the microbiota influences the host epigenome. Specifically, DNA methylation of the 5ʹ CpG Island in the toll-like receptor 4 (Tlr4) gene was decreased in large intestinal IECs from GF mice compared to conventionally housed (CNV) mice, resulting in reduced Tlr4 expression and responsiveness to the pathogen-associated molecular pattern lipopolysaccharide (LPS).22 Demethylation was also detected at the chemokine ligand Cxcl16 gene in the colon and lungs of GF mice compared to CNV mice, which is consistent with decreased mucosal invariant natural killer T cell accumulation in absence of the microbiota.23 Microbiota also directed DNA methylation in regulatory T cells (Tregs) by increasing expression of Uhrf1, a DNA methylation adaptor protein that complexes with Dnmt1 and HDAC1.24 T-cell specific deletion of Uhrf1 impaired normal cell cycle gene expression in Tregs and consequently led to spontaneous colitis.
In vitro and in silico β-lactamase inhibitory properties and phytochemical profile of Ocimum basilicum cultivated in central delta of Egypt
Published in Pharmaceutical Biology, 2022
Nagwa A. Shoeib, Lamiaa A. Al-Madboly, Amany E. Ragab
The 1H NMR spectrum (provided in supplementary file) indicated the presence of five aromatic protons suggesting a monosubstituted benzene ring. The 13C NMR spectrum (provided in supplementary file) showed eight signals accounting for 10 carbons. The aromatic carbons were represented by chemical shifts at δC 134.3 (C1), 128.8 (C2,6), 130.2 (C3,5) and 128.1 (C4), while the olefinic carbons (C7 and C8) exhibited chemical shifts at δC 117.2 and 144.9. Signals for carbonyl group at 167.8 (C9) and for deshielded alkyl carbon at δC 50.8 (C10) indicated an ester group. A methyl group peak at δH 3.79 confirmed a methyl ester. These spectral data are in good concordance with those in the literature for methyl cinnamate. The stereochemistry was identified as E based on the coupling constant for the trans protons JH7–H8=16 Hz (Spekreijse et al. 2012; Sitrallah et al. 2016).