Nucleosome remodeling complexes comprise several large families of chromatin modifiers that integrate multiple epigenetic control signals to play key roles in cell type-specific transcription regulation. We previously isolated a methyl-binding domain protein 2 (MBD2)-containing nucleosome remodeling and deacetylation (NuRD) complex from primary erythroid cells and showed that MBD2 contributes to DNA methylation-dependent embryonic and fetal β-type globin gene silencing during development in vivo. Here we present structural and biophysical details of the coiledcoil interaction between MBD2 and p66α, a critical component of the MBD2-NuRD complex. We show that enforced expression of the isolated p66α coiled-coil domain relieves MBD2-mediated globin gene silencing and that the expressed peptide interacts only with a subset of components of the MBD2-NuRD complex that does not include native p66α or Mi-2. These results demonstrate the central importance of the coiled-coil interaction and suggest that MBD2-dependent DNA methylation-driven gene silencing can be disrupted by selectively targeting this coiled-coil complex.epigenetics | gene regulation D NA methylation involves the enzymatic addition of a methyl group at the C5 position of symmetrically opposed cytosine bases in a double-stranded cytosine-guanosine sequence (CpG). Regions of increased CpG content (CpG islands) often are found associated with promoters and, when methylated, silence expression of the associated gene (1, 2). Although most CpG islands are largely unmethylated in normal adult tissues, a subset of CpG islands is methylated in specific tissue subtypes, stages of differentiation, and development. Importantly, hypermethylation and silencing of tumor suppressor genes represents a pro-oncogenic change found in a wide range of malignancies (3). These observations have raised interest in DNA methylation as both an important genetic regulatory mechanism and a potential therapeutic target for either re-expression of developmentally silenced genes or reversing tumor suppressor gene silencing in cancer (4, 5).The methyl cytosine binding proteins include a family that specifically recognizes the methylated CpG sequence through an ∼60 amino acid methyl-binding domain (MBD). There are five members of the MBD family in mammals: methyl CpG-binding protein 2 (MeCP2), the first to be identified (6), and MBD1 through MBD4 (7). We and others have isolated and characterized an MBD2-containing nucleosome remodeling and deacetylation (NuRD) complex (referred to as "MBD2-NuRD") that binds methylated DNA and regulates transcription of the associated gene (8-10). The MBD2-NuRD complex comprises at least one homolog of six core proteins: MBD2, retinoblastoma protein-associated protein (RbAp46 or -48) Mi-2(α or β), p66(α or β), histone deacetylase (HDAC1 or 2), and metastasis associated (MTA1 or -2) (Fig. 1A). However, the specific interactions involved in the formation of the MBD2-NuRD complex have not been delineated clearly; information that is key to understanding (i) ...

Psychological stress has been proposed as a major contributor to the progression of cardiovascular disease (CVD). Acute mental stress can activate the sympathetic-adrenal-medullary (SAM) axis, eliciting the release of catecholamines (NE and EPI) resulting in the elevation of heart rate (HR) and blood pressure (BP). Combined stress (psychological and physical) can exacerbate these cardiovascular responses, which may partially contribute to the elevated risk of CVD and increased proportionate mortality risks experienced by some occupations (e.g., firefighting and law enforcement). Studies have supported the benefits of physical activity on physiological and psychological health, including the cardiovascular response to acute stress. Aerobically trained individuals exhibit lower sympathetic nervous system (e.g., HR) reactivity and enhanced cardiovascular efficiency (e.g., lower vascular reactivity and decreased recovery time) in response to physical and/or psychological stress. In addition, resistance training has been demonstrated to attenuate cardiovascular responses and improve mental health. This review will examine stress-induced cardiovascular reactivity and plausible explanations for how exercise training and physical fitness (aerobic and resistance exercise) can attenuate cardiovascular responses to stress. This enhanced functionality may facilitate a reduction in the incidence of stroke and myocardial infarction. Finally, this review will also address the interaction of obesity and physical activity on cardiovascular reactivity and CVD.

The epigenetic code of DNA methylation is interpreted chiefly by methyl cytosine binding domain (MBD) proteins which in turn recruit multiprotein co-repressor complexes. We previously isolated one such complex, MBD2-NuRD, from primary erythroid cells and have shown it contributes to embryonic/fetal β-type globin gene silencing during development. This complex has been implicated in silencing tumor suppressor genes in a variety of human tumor cell types. Here we present structural details of chicken MBD2 bound to a methylated DNA sequence from the ρ-globin promoter to which it binds in vivo and mediates developmental transcriptional silencing in normal erythroid cells. While previous studies have failed to show sequence specificity for MBD2 outside of the symmetric mCpG, we find that this domain binds in a single orientation on the ρ-globin target DNA sequence. Further, we show that the orientation and affinity depends on guanine immediately following the mCpG dinucleotide. Dynamic analyses show that DNA binding stabilizes the central β-sheet, while the N- and C-terminal regions of the protein maintain mobility. Taken together, these data lead to a model in which DNA binding stabilizes the MBD2 structure and that binding orientation and affinity is influenced by the DNA sequence surrounding the central mCpG.

The MBD2-NuRD (Nucleosome Remodeling and Deacetylase) complex is an epigenetic reader of DNA methylation that regulates genes involved in normal development and neoplastic diseases. To delineate the architecture and functional interactions of the MBD2-NuRD complex, we previously solved the structures of MBD2 bound to methylated DNA and a coiled-coil interaction between MBD2 and p66α that recruits the CHD4 nucleosome remodeling protein to the complex. The work presented here identifies novel structural and functional features of a previously uncharacterized domain of MBD2 (MBD2IDR). Biophysical analyses show that the MBD2IDR is an intrinsically disordered region (IDR). However, despite this inherent disorder, MBD2IDR increases the overall binding affinity of MBD2 for methylated DNA. MBD2IDR also recruits the histone deacetylase core components (RbAp48, HDAC2 and MTA2) of NuRD through a critical contact region requiring two contiguous amino acid residues, Arg286 and Leu287. Mutating these residues abrogates interaction of MBD2 with the histone deacetylase core and impairs the ability of MBD2 to repress the methylated tumor suppressor gene PRSS8 in MDA-MB-435 breast cancer cells. These findings expand our knowledge of the multi-dimensional interactions of the MBD2-NuRD complex that govern its function.

Obesity-related oxidative stress, the imbalance between pro-oxidants and antioxidants (e.g., nitric oxide), has been linked to metabolic and cardiovascular disease, including endothelial dysfunction and atherosclerosis. Reactive oxygen species (ROS) are essential for physiological functions including gene expression, cellular growth, infection defense, and modulating endothelial function. However, elevated ROS and/or diminished antioxidant capacity leading to oxidative stress can lead to dysfunction. Physical activity also results in an acute state of oxidative stress. However, it is likely that chronic physical activity provides a stimulus for favorable oxidative adaptations and enhanced physiological performance and physical health, although distinct responses between aerobic and anaerobic activities warrant further investigation. Studies support the benefits of dietary modification as well as exercise interventions in alleviating oxidative stress susceptibility. Since obese individuals tend to demonstrate elevated markers of oxidative stress, the implications for this population are significant. Therefore, in this review our aim is to discuss (i) the role of oxidative stress and inflammation as associated with obesity-related diseases, (ii) the potential concerns and benefits of exercise-mediated oxidative stress, and (iii) the advantageous role of dietary modification, including acute or chronic caloric restriction and vitamin D supplementation.