26 research outputs found
Characterization of DNA with an 8-oxoguanine modification
The oxidation of DNA resulting from reactive oxygen species generated during aerobic respiration is a major cause of genetic damage that, if not repaired, can lead to mutations and potentially an increase in the incidence of cancer and aging. A major oxidation product generated in cells is 8-oxoguanine (oxoG), which is removed from the nucleotide pool by the enzymatic hydrolysis of 8-oxo-2′-deoxyguanosine triphosphate and from genomic DNA by 8-oxoguanine-DNA glycosylase. Finding and repairing oxoG in the midst of a large excess of unmodified DNA requires a combination of rapid scanning of the DNA for the lesion followed by specific excision of the damaged base. The repair of oxoG involves flipping the lesion out of the DNA stack and into the active site of the 8-oxoguanine-DNA glycosylase. This would suggest that thermodynamic stability, in terms of the rate for local denaturation, could play a role in lesion recognition. While prior X-ray crystal and NMR structures show that DNA with oxoG lesions appears virtually identical to the corresponding unmodified duplex, thermodynamic studies indicate that oxoG has a destabilizing influence. Our studies show that oxoG destabilizes DNA (ΔΔG of 2–8 kcal mol−1 over a 16–116 mM NaCl range) due to a significant reduction in the enthalpy term. The presence of oxoG has a profound effect on the level and nature of DNA hydration indicating that the environment around an oxoG•C is fundamentally different than that found at G•C. The temperature-dependent imino proton NMR spectrum of oxoG modified DNA confirms the destabilization of the oxoG•C pairing and those base pairs that are 5′ of the lesion. The instability of the oxoG modification is attributed to changes in the hydrophilicity of the base and its impact on major groove cation binding
Sex- and age-related differences in the management and outcomes of chronic heart failure: an analysis of patients from the ESC HFA EORP Heart Failure Long-Term Registry
Aims: This study aimed to assess age- and sex-related differences in management and 1-year risk for all-cause mortality and hospitalization in chronic heart failure (HF) patients. Methods and results: Of 16 354 patients included in the European Society of Cardiology Heart Failure Long-Term Registry, 9428 chronic HF patients were analysed [median age: 66 years; 28.5% women; mean left ventricular ejection fraction (LVEF) 37%]. Rates of use of guideline-directed medical therapy (GDMT) were high (angiotensin-converting enzyme inhibitors/angiotensin receptor blockers, beta-blockers and mineralocorticoid receptor antagonists: 85.7%, 88.7% and 58.8%, respectively). Crude GDMT utilization rates were lower in women than in men (all differences: P\ua0 64 0.001), and GDMT use became lower with ageing in both sexes, at baseline and at 1-year follow-up. Sex was not an independent predictor of GDMT prescription; however, age >75 years was a significant predictor of GDMT underutilization. Rates of all-cause mortality were lower in women than in men (7.1% vs. 8.7%; P\ua0=\ua00.015), as were rates of all-cause hospitalization (21.9% vs. 27.3%; P\ua075 years. Conclusions: There was a decline in GDMT use with advanced age in both sexes. Sex was not an independent predictor of GDMT or adverse outcomes. However, age >75 years independently predicted lower GDMT use and higher all-cause mortality in patients with LVEF 6445%
Identification of Two Homozygous Variants in MYBPC3 and SMYD1 Genes Associated with Severe Infantile Cardiomyopathy
Mutations in cardiac genes are one of the primary causes of infantile cardiomyopathy. In this study, we report the genetic findings of two siblings carrying variations in the MYBPC3 and SMYD1 genes. The first patient is a female proband exhibiting hypertrophic cardiomyopathy (HCM) and biventricular heart failure carrying a truncating homozygous MYBPC3 variant c.1224-52G>A (IVS13-52G>A) and a novel homozygous variant (c.302A>G; p.Asn101Ser) in the SMYD1 gene. The second patient, the proband’s sibling, is a male infant diagnosed with hypertrophic cardiomyopathy and carries the same homozygous MYBPC3 variant. While this specific MYBPC3 variant (c.1224-52G>A, IVS13-52G>A) has been previously reported to be associated with adult-onset hypertrophic cardiomyopathy, this is the first report linking it to infantile cardiomyopathy. In addition, this work describes, for the first time, a novel SMYD1 variant (c.302A>G; p.Asn101Ser) that has never been reported. We performed a histopathological evaluation of tissues collected from both probands and show that these variants lead to myofibrillar disarray, reduced and irregular mitochondrial cristae and cardiac fibrosis. Together, these results provide critical insight into the molecular functionality of these genes in human cardiac physiology
Site-Specific Stabilization of DNA by a Tethered Major Groove Amine, 7‑Aminomethyl-7-deaza-2′-deoxyguanosine
A cationic
7-aminomethyl-7-deaza-2′-deoxyguanosine (7amG)
was incorporated site-specifically into the self-complementary duplex
d(G<sup>1</sup>A<sup>2</sup>G<sup>3</sup>A<sup>4</sup><u>X</u><sup>5</sup>C<sup>6</sup>G<sup>7</sup>C<sup>8</sup>T<sup>9</sup>C<sup>10</sup>T<sup>11</sup>C<sup>12</sup>)<sub>2</sub> (<u>X</u> = 7amG). This construct placed two positively charged amines adjacent
to the major groove edges of two symmetry-related guanines, providing
a model for probing how cation binding in the major groove modulates
the structure and stability of DNA. Molecular dynamics calculations
restrained by nuclear magnetic resonance (NMR) data revealed that
the tethered cationic amines were in plane with the modified base
pairs. The tethered amines did not form salt bridges to the phosphodiester
backbone. There was also no indication of the amines being capable
of hydrogen bonding to flanking DNA bases. NMR spectroscopy as a function
of temperature revealed that the X<sup>5</sup> imino resonance remained
sharp at 55 °C. Additionally, two 5′-neighboring base
pairs, A<sup>4</sup>:T<sup>9</sup> and G<sup>3</sup>:C<sup>10</sup>, were stabilized with respect to the exchange of their imino protons
with solvent. The equilibrium constant for base pair opening at the
A<sup>4</sup>:T<sup>9</sup> base pair determined by magnetization
transfer from water in the absence and presence of added ammonia base
catalyst decreased for the modified duplex compared to that of the
A<sup>4</sup>:T<sup>9</sup> base pair in the unmodified duplex, which
confirmed that the overall fraction of the A<sup>4</sup>:T<sup>9</sup> base pair in the open state of the modified duplex decreased. This
was also observed for the G<sup>3</sup>:C<sup>10</sup> base pair,
where α<i>K</i><sub>op</sub> for the G<sup>3</sup>:C<sup>10</sup> base pair in the modified duplex was 3.0 × 10<sup>6</sup> versus 4.1 × 10<sup>6</sup> for the same base pair in
the unmodified duplex. In contrast, equilibrium constants for base
pair opening at the X<sup>5</sup>:C<sup>8</sup> and C<sup>6</sup>:G<sup>7</sup> base pairs did not change at 15 °C. These results argue
against the notion that electrostatic interactions with DNA are entirely
entropic and suggest that major groove cations can stabilize DNA via
enthalpic contributions to the free energy of duplex formation
Transcriptional regulation by methyltransferases and their role in the heart: highlighting novel emerging functionality
Correction to Differential Stabilities and Sequence-Dependent Base Pair Opening Dynamics of Watson–Crick Base Pairs with 5-Hydroxymethylcytosine, 5-Formylcytosine, or 5-Carboxylcytosine
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Histone methyltransferase Smyd1 regulates mitochondrial energetics in the heart
Smyd1, a muscle-specific histone methyltransferase, has established roles in skeletal and cardiac muscle development, but its role in the adult heart remains poorly understood. Our prior work demonstrated that cardiac-specific deletion of Smyd1 in adult mice (Smyd1-KO) leads to hypertrophy and heart failure. Here we show that down-regulation of mitochondrial energetics is an early event in these Smyd1-KO mice preceding the onset of structural abnormalities. This early impairment of mitochondrial energetics in Smyd1-KO mice is associated with a significant reduction in gene and protein expression of PGC-1α, PPARα, and RXRα, the master regulators of cardiac energetics. The effect of Smyd1 on PGC-1α was recapitulated in primary cultured rat ventricular myocytes, in which acute siRNA-mediated silencing of Smyd1 resulted in a greater than twofold decrease in PGC-1α expression without affecting that of PPARα or RXRα. In addition, enrichment of histone H3 lysine 4 trimethylation (a mark of gene activation) at the PGC-1α locus was markedly reduced in Smyd1-KO mice, and Smyd1-induced transcriptional activation of PGC-1α was confirmed by luciferase reporter assays. Functional confirmation of Smyd1's involvement showed an increase in mitochondrial respiration capacity induced by overexpression of Smyd1, which was abolished by siRNA-mediated PGC-1α knockdown. Conversely, overexpression of PGC-1α rescued transcript expression and mitochondrial respiration caused by silencing Smyd1 in cardiomyocytes. These findings provide functional evidence for a role of Smyd1, or any member of the Smyd family, in regulating cardiac energetics in the adult heart, which is mediated, at least in part, via modulating PGC-1α