Guanine-rich sequences from the regulatory region of the RANKL gene, which plays an important role in the occurrence of osteoporosis, can fold into the G-quadruplex structure, thereby affecting the expression of the gene. The 20 nucleotide sequence folds into an antiparallel, two-quartet G-quadruplex, stabilized with A-G-A and G-G-G base triads, although four G-tracts with three successive guanins could be expected to form G-quadruplex with three G-quartets. Use of NMR spectroscopy enabled us to determine 3D structure of RAN4 and show that the structure with two G-quartets is dependent on adenine A5 from the A-G-A base triad. Knowing the switching mechanism between the two structures contributes to understanding the influence of nucleotides from the loops on the stability and folding of G-quadruplexes, which can be exploited for predictions of the structures formed by guanine-rich sequences and to improve the design of small molecules that bind G-quadruplexes and thereby affect their cell function.
COBISS.SI-ID: 6525722
Molecular crowding conditions provided by high concentration of cosolutes are utilized for characterization of biomolecules in cell-mimicking environment and development of drug-delivery systems. In this context, (poly)ethylene glycols are often used for studying non-canonical DNA structures termed G-quadruplexes, which came into focus by emerging structural biology findings and new therapeutic drug design approaches. Recently, several reports were made arguing against using (poly)ethylene glycols in role of molecular crowding agents due to their direct impact on DNA G-quadruplex stability and topology. However, the available data on structural details underlying DNA interaction is very scarce and thus limits in-depth comprehension. Herein, structural and thermodynamic analyses were strategically combined to assess G-quadruplex-cosolute interactions and address previously reported variances regarding the driving forces of G-rich DNA structural transformations undermolecular crowding conditions. With the use of complementary (CD, NMR and UV) spectroscopicmethods andmodel approach we characterized DNA G-quadruplex in the presence of the smallest and one of the largest typically used (poly)ethylene glycols. Dehydration effect is the key contributor to ethylene-glycol-induced increased stability of the G-quadruplex, which is in the case of the large cosolute mainly guided by the subtle direct interactions between PEG 8000 and the outer G-quartet regions.
COBISS.SI-ID: 6389786
Epigenetic mechanisms including posttranslational histone modifications and DNA methylation are emerging as important determinants of bone homeostasis. With our case-control study we aimed to identify which chromatin-modifying enzymes could be involved in the pathology of postmenopausal osteoporosis and osteoarthritis while co-regulated by estrogens, oxidative stress and hypoxia. Gene expression of HAT1, KAT5, HDAC6, MBD1 and DNMT3A affected by oxidative stress and hypoxia in an in vitro qPCR screening step performed on an osteoblast cell line was analysed in trabecular bone tissue samples from 96 patients. Their expression was significantly reduced in patients with postmenopausal osteoporosis and osteoarthritis as compared to autopsy controls and significantly correlated with bone mineral density and several bone histomorphometry-derived parameters of bone quality and quantity as well as indicators of oxidative stress, RANK/RANKL/OPG system and angiogenesis. Furthermore, oxidative stress increased DNA methylation levels at the RANKL and OPG promoters while decreasing histone acetylation levels at these two genes. Our study is the first to show that higher expression of HAT1, HDAC6 and MBD1 is associated with superior quantity as well as quality of the bone tissue having a more favourable trabecular structure.
COBISS.SI-ID: 4627057
To identify genetic determinants of susceptibility to clinical vertebral fractures, which is an important complication of osteoporosis. Here we conduct a genome-wide association study in 1553 postmenopausal women with clinical vertebral fractures and 4340 controls, with a two-stage replication involving 1028 cases and 3762 controls. Potentially causal variants were identified using expression quantitative trait loci (eQTL) data from transiliac bone biopsies and bioinformatic studies. A locus tagged by rs10190845 was identified on chromosome 2q13, which was significantly associated with clinical vertebral fracture (P=1.04%10%9) with a large effect size (OR 1.74, 95%%CI 1.06 to 2.6). Bioinformatic analysis of this locus identified several potentially functional SNPs that are associated with expression of the positional candidate genes TTL (tubulin tyrosine ligase) and SLC20A1 (solute carrier family 20 member 1). Three other suggestive loci were identified on chromosomes 1p31, 11q12 and 15q11. All these loci were novel and had not previously been associated with bone mineral density or clinical fractures. We have identified a novel genetic variant that is associated with clinical vertebral fractures by mechanisms that are independent of BMD. Further studies are now in progress to validate this association and evaluate the underlying mechanism.
COBISS.SI-ID: 4456049
Abstract Background: Severe trauma continues to represent a global public health issue and mortality and morbidity in trauma patients remains substantial. A number of initiatives have aimed to provide guidance on the management of trauma patients. This document focuses on the management of major bleeding and coagulopathy following trauma and encourages adaptation of the guiding principles to each local situation and implementation within each institution. Methods: The pan-European, multidisciplinary Task Force for Advanced Bleeding Care in Trauma was founded in 2004 and included representatives of six relevant European professional societies. The group used a structured, evidence-based consensus approach to address scientific queries that served as the basis for each recommendation and supporting rationale. Expert opinion and current clinical practice were also considered, particularly in areas in which randomised clinical trials have not or cannot be performed. Existing recommendations were reconsidered and revised based on new scientific evidence and observed shifts in clinical practice; new recommendations were formulated to reflect current clinical concerns and areas in which new research data have been generated. This guideline represents the fourth edition of a document first published in 2007 and updated in 2010 and 2013.
COBISS.SI-ID: 757667