Impact of Interactions between Su(Hw)-Dependent Insulators on the Transvection Effect in Drosophila melanogaster.

Transvection is a phenomenon of interallelic communication in which enhancers can activate a specific promoter located on a homologous chromosome. Insulators play a significant role in ensuring functional interactions between enhancers and promoters. In the presented work, we created a model where two or three copies of the insulator are located next to enhancers and promoters localized on homologous chromosomes. Using the Su(Hw) insulator as a model, we showed that the functional interaction between a pair of insulators promotes enhancer-promoter trans-interactions. The interaction between the three insulators, on the contrary, can lead to the formation of chromatin loops that sterically hinder the full enhancer-promoter interaction. The results of the work suggest the participation of insulators in the regulation of homologous chromosome pairing and in communication between distant genomic loci.

The BEAF-32 Protein Directly Interacts with Z4/putzig and Chriz/Chromator Proteins in Drosophila melanogaster.

In Drosophila, the BEAF-32, Z4/putzig, and Chriz/Chromator proteins colocalize in the interbands of polytene chromosomes. It was assumed that these proteins can form a complex that affects the structure of chromatin. However, the mechanism of the formation of such a complex has not been studied. We have proved for the first time that the BEAF-32, Z4/putzig, and Chriz/Chromator proteins interact directly with each other and localized the protein domains that provide multiple protein-protein interactions. Based on the data obtained, we developed a model of the mechanism of the formation the BEAF/Z4/Chriz complex and its recruitment to chromatin.

The Chriz Protein Promotes the Recruitment of the Z4 Protein to the STAT-Dependent Promoters.

Proteins Z4/putzig and Chriz/Chromator are involved in the chromatin organization on the promoters of the majority of Drosophila genes. It was shown that the Chriz protein region from aa 273 to 503 is required for the interaction with the Z4 protein. Deletion of this sequence leads to derepression of a number of STAT-dependent genes and development of melanotic tumors in flies. The results of this study suggest that the Chriz protein promotes the recruitment of the Z4 protein to chromatin.

The Functions and Mechanisms of Action of Insulators in the Genomes of Higher Eukaryotes.

The mechanisms underlying long-range interactions between chromatin regions and the principles of chromosomal architecture formation are currently under extensive scrutiny. A special class of regulatory elements known as insulators is believed to be involved in the regulation of specific long-range interactions between enhancers and promoters. This review focuses on the insulators of Drosophila and mammals, and it also briefly characterizes the proteins responsible for their functional activity. It was initially believed that the main properties of insulators are blocking of enhancers and the formation of independent transcription domains. We present experimental data proving that the chromatin loops formed by insulators play only an auxiliary role in enhancer blocking. The review also discusses the mechanisms involved in the formation of topologically associating domains and their role in the formation of the chromosomal architecture and regulation of gene transcription.

Activation of Su(Hw)-Controlled Genes Is Associated with Increase in GAF Binding.

The interaction of the GAF protein with the promoters of neuron-specific genes during activation and repression of transcription was studied. We showed that, while the Su(Hw) protein remains stably associated with the promoters of these genes at different transcriptional state, the GAF protein level is significantly higher when transcription is activated.

Studying Interactions between the Mod(mdg4)-67.2 Protein and Other Mod(mdg4) Isoforms in the Embryonic Cells of Drosophila melanogaster.

It is found that, in embryonic D. melanogaster cells, Mod(mdg4) protein isoforms can interact with each other through BTB domains. However, this nonspecific interaction is destroyed as a result of recruitment of protein complexes to the chromatin sites.

[Polymorphism A1166C of AGTR1 Gene and the State of Intrarenal Blood Flow in Patients with Essential Arterial Hypertension 1-2 Degrees].

AIM: to study relationship between genetic disorders and features of intrarenal blood flow in patients with essential arterial hypertension (AH) of 1-2 degree. MATERIALS AND METHODS: We examined 100 patients (60 women, 40 men) aged 35 to 58 years with 1-2­degree essential arterial hypertension (AH) and chronic kidney disease (CKD) stages I-III. Examination included triplex scanning of renal arteries on the ultrasound scanner Vivid-7 Dimension, genotyping of single-nucleotide polymorphism А1166С of the AGTR1 gene by real time polymerase chain reaction (PCR), estimation of glomerular filtration rate (GFR) using CKD-EPI formula. Patients were divided into 2 groups: group 1 included persons with I and II stage CKD (n=65, 25 men and 40 women), group 2 included patients with stages IIIA and IIIB CKD (n=35, 15 men and 20 women). RESULTS: Among patients of group 1 prevailed genotype AA, while among group 2 patients prevailed genotype AC. Speed of blood flow in interlobar renal arteries was higher in the group 1 compared with group 2, while in the group 2 time of acceleration of blood flow was higher than in the group 1. DISCUSSION: The data obtained are indicative of the decrease of systolic, diastolic, and averaged maximal blood flow velocity and the lengthening of acceleration time in patients with higher CKD stage. CONCLUSIONS: The presence in the genotype of patients with 1-2­degree AH of AGTR1 1166С allele may be considered a risk factor of early development of CKD. Lowering of speed characteristics of blood flow and lengthening of the acceleration time in patients with AH can be a criterion of hypertensive nephropathy development.

[Comparative characteristics of the chemical composition of vitreal contents of cadaver eyes and eyes with terminal refractory glaucoma]. / Sravnitel'naia kharakteristika khimicheskogo sostava vitreal'nogo soderzhimogo kadavernykh glaz i glaz s refrakternoi terminal'noi glaukomoi.

PURPOSE: To compare the chemical elemental composition of vitreous cavity content taken from cadaveric eyes compared to samples taken from the eyes with terminal stage refractory glaucoma with decompensated intraocular pressure (IOP). MATERIAL AND METHODS: The vitreous contents of the eyes from 2 groups were studied. The 1st group included 15 cadaveric eyes; the 2nd group included 15 eyes with refractory glaucoma in the terminal stage of the disease with decompensated IOP in patients with hypertension pain. The vitreal content samples were taken in the course of antiglaucoma surgery aimed at preserving the eye as an organ and involving employment of drainage in the vitreous cavity. The study of virtual contents was carried out on energy dispersive spectrometer Oxford X-Max 50 integrated into scanning electron microscope Zeiss EVO LS10. RESULTS: Increased concentrations of Kalium and Phosphorus were detected in the vitreous content of cadaveric eyes compared with the vitreal content from the eyes with terminal glaucoma with decompensated IOP taken in vivo (K - 0.172/0.093; P - 0.045/0.025 mmol/L). In the vitreous cavity in the eyes with end-stage glaucoma with decompensated IOP, the concentration of Nitrogen was higher in comparison with human cadaver eyes (2.030/1.424 mmol/L). CONCLUSION: The increased concentrations of Kalium and Phosphorus in the vitreous content of cadaveric eyes is associated with postmortem autolytic processes and with the release of intracellular content in the destruction of cell membranes. The increased Nitrogen concentration in the vitreal contents of the eyes with terminal stage glaucoma with decompensated IOP may be associated with the presence of osmotically active nitrogen-containing compounds in the eyes with increased IOP.

The Role of GC-Rich Sequences from the Promoter Region of the Drosophila melanogaster yellow Gene in the Enhancer- Dependent Activation of Transcription.

It is shown that mutations in two GC-rich sequences (GC-boxes) from the promoter region of the yellow gene during enhancer-dependent transcription activation do not affect the basal level of the yellow gene transcription but destabilize the interaction between the enhancers and the promoter.

[Influence of chemical compositions of anterior chamber aqueous humour and blood serum on the secretion of intraocular fluid]. / Vliianie khimicheskogo sostava vlagi perednei kamery glaza i syvorotki krovi na sekretsiiu vnutriglaznoi zhidkosti.

PURPOSE: to identify the standard chemical composition of anterior chamber aqueous humour (AH) using energy dispersive spectrometer (EDS) integrated in scanning electron microscope (SEM); to study the influence of concentration gradient of chemical elements between aqueous humor and blood serum (BS) on the secretion of intraocular fluid (IOF) at normal and increased intraocular pressure (IOP). MATERIAL AND METHODS: The study involved two groups of patients consisting of 33 people (33 eyes) each. The 1st group included patients with cataract and normal IOP (control), the 2nd group included patients with POAG and decompensated IOP. The samples (AH and BS) were taken during surgeries and studied using Oxford X-Max50 EDS integrated in EVO LS10 SEM. RESULTS: The concentration ratios (mmol/l) of AH/BS for Na at normal IOP was 1.472/1.278, for K - 0.106/0.035. In cases with POAG with decompensated IOP, the concentration ratio of Na was 1.424/1.248, K - 0.114/0.036. The concentration ratio of N between AH in cases with decompensated IOP and AH of normotonic eyes was 1.151/0.960, for S - 0.020/0.012. CONCLUSION: Consistent excess of Na and K concentrations in AH compared to BS indicates active participation of these osmotically active elements in the normal process of intraocular fluid secretion. The absence of significant differences in the ratios of Na and K in AH and BS at normal and decompensated IOP indicates low significance of these elements for pathological hypersecretion of intraocular fluid. Increased concentration of N in AH eyes with decompensated IOP compared with AH at normal IOP indicates possible involvement of nitrogen-containing osmotically active substances in the abnormal hypersecretion of intraocular fluid.

Mapping the D.melanogaster En1A Enhancer Modules Responsible for Transcription Activation and Long-Distance Enhancer-Promoter Interactions.

The structure of the new enhancer En1A of the 1A region of the X chromosome of D. melanogaster was investigated. Two distinct regulatory elements were found. The first element is responsible for transcription activation, and the second element provides specific interaction with the promoter of the yellow gene. The findings support the hypothesis of a modular structure for enhancers, including certain sequences that bind transcription activators and special communication elements providing long-distance enhancer-promoter interaction.

LTR sequence of the MDG4 retrotransposon contains the MAD protein binding site that affects the east-dependent repression.

Earlier, we showed in a model system of the yellow gene of D. melanogaster that an increase in the EAST protein concentration leads to repression in bristles, the mechanism of which remained obscure. In this study, an inverted repeat was localized by genetic methods in the long terminal repeat (LTR) sequence of the MDG4 retrotransposon. This repeat includes the binding site for the Mad protein-the key component of the of TGF-ß/BMP signaling cascade. The results of this work suggest that the Mad protein recruits to chromatin a regulatory complex that functionally interacts with the EAST protein. This complex either itself suppresses the yellow gene expression in bristles or moves the transgene to the nuclear regions with a high concentration of transcription repression factors.

Zinc finger domain of Su(Hw) protein is required for the formation of functional Su(Hw)-dependent insulator complex.

This study is devoted to clarifying the role of Mod(mdg4)-67.2 and Su(Hw) proteins in the interaction between Su(Hw)-dependent insulator complexes and identifying the specific domains of the Su(Hw) protein required for insulation or mutual neutralization of insulators. Using genetic techniques and experiments in yeast two-hybrid system, we have demonstrated that the zinc finger domain of the Su(Hw) protein is involved in forming a functional insulator complex and cannot be replaced with the DNA-binding domain of the GAL4 protein.

Mod(mdg4)-58.8, isoform of mod(mdg4) loci, directly interacts with MTACP1A and MTACP1B proteins of Drosophila melanogaster.

As a result of experiments in yeast two-hybrid system, coimmunoprecipitation of proteins from D. melanogaster embryo cell lysate, and immunostaining, it was shown for the first time that Mod(mdg4)-58.8 protein (isoform P), a product of mod(mdg4) locus, directly interacts with mtACP1A and mtACP1B proteins. These proteins are involved in de novo biosynthesis of fatty acids in mitochondria and are required for normal gametogenesis in males and females and, possibly, for the trachea development. This result expands the understanding of the role of mod(mdg4) locus products in the regulation of life activity of the eukaryotic cell.

Effect of iron oxide loading on magnetoferritin structure in solution as revealed by SAXS and SANS.

Synthetic biological macromolecule of magnetoferritin containing an iron oxide core inside a protein shell (apoferritin) is prepared with different content of iron. Its structure in aqueous solution is analysed by small-angle synchrotron X-ray (SAXS) and neutron (SANS) scattering. The loading factor (LF) defined as the average number of iron atoms per protein is varied up to LF=800. With an increase of the LF, the scattering curves exhibit a relative increase in the total scattered intensity, a partial smearing and a shift of the match point in the SANS contrast variation data. The analysis shows an increase in the polydispersity of the proteins and a corresponding effective increase in the relative content of magnetic material against the protein moiety of the shell with the LF growth. At LFs above ∼150, the apoferritin shell undergoes structural changes, which is strongly indicative of the fact that the shell stability is affected by iron oxide presence.