[CRISPR/Cas9-editing-based modeling of hypoxia in renal cancer cells].

Uncontrolled growth in the cell mass of malignant tumors induces intensive angiogenesis. However, the demands of the cancer cells for nutrients and oxygen remain only partially met. Hypoxia is a process that accompanies malignant transformation and evokes changes in the DNA methylation profile in solid tumors. To a certain extent, these changes, including the hypermethylation of tumor suppressor gene promoters, are related to the decrease in the activity of Tet proteins under the conditions of oxygen and free radical deficit. Stabilization, accumulation, and nuclear translocation of the transcription factor HIF1α are the key molecular events in hypoxia. We modified the clear-cell renal cancer cell line Caki1 to stabilize the HIF1α protein and characterized a model cell line that will enable the studies of the mechanisms of changes of the DNA methylation level at a constant activity of Tet proteins and a gene transcription profile characteristic of hypoxia. The CRISPR/Cas9 DNA editing system was used to edit the VHL gene. The mutant VHL protein contained a disrupted alpha-helix at the C-terminus and could not participate in the molecular pathway of proteasomal degradation of the HIF1α factor; therefore, the latter accumulated in the nucleus and activated the specific target genes. An analysis of gene transcription revealed the induction of hypoxia-associated genes in the modified cell line. The developed Сaki-1/VHLmut model can be used to discriminate between the effects evoked by oxygen-suppressed hydroxylases of the Tet family and other hypoxia-associated mechanisms of DNA methylation/demethylation.

Modeling myocardial infarction in mice: methodology, monitoring, pathomorphology.

Myocardial infarction is one of the most serious and widespread diseases in the world. In this work, a minimally invasive method for simulating myocardial infarction in mice is described in the Russian Federation for the very first time; the procedure is carried out by ligation of the coronary heart artery or by controlled electrocoagulation. As a part of the methodology, a series of anesthetic, microsurgical and revival protocols are designed, owing to which a decrease in the postoperational mortality from the initial 94.6 to 13.6% is achieved. ECG confirms the development of large-focal or surface myocardial infarction. Postmortal histological examination confirms the presence of necrosis foci in the heart muscles of 87.5% of animals. Altogether, the medical data allow us to conclude that an adequate mouse model for myocardial infarction was generated. A further study is focused on the standardization of the experimental procedure and the use of genetically modified mouse strains, with the purpose of finding the most efficient therapeutic approaches for this disease.

[Bifunctional role of domain zinc fingers of methyl-DNA-binding protein Kaiso].

DNA methylation in mammals is one of the major epigenetic mark that associates with inactive chromatin state. Methyl-DNA-binding proteins bind methylated DNA and silence gene transcription by recruiting repression complexes. Kaiso is one of the methyl-DNA-binding proteins. It has a domain structure: N-terminal BTB/POZ domain involved in protein-protein interaction and C-terminal zinc-fingers of C2H2 type that bind methylated DNA (mCGmCG) or nonmethylated - TCCTGCNA. Here we show that Kaiso interacts with p120 catenin through zinc finger 2 and 3. This interaction has dual consequences. Firstly, binding to p120 inhibits nuclear import of Kaiso that results in most of Kaiso-p120 complexes becoming cytoplasmic. And secondly, bound p120 makes impossible interaction of the zinc fingers with methylated DNA. These modes of Kaiso modulation by p120 can open attractive perspectives in linking events on cell membrane and changes in nuclear gene expression.