Vol 58, No 2 (2024)

Uveal melanoma (UM) is a tumor of neuroectodermal origin, which results from malignant transformation of melanocytes of the eye vasculature: iris, ciliary body and chorioidea. UM represents up to 5% of all melanoma cases, but it is extremely aggressive, since half of patients with UM develop metastases within the first 1‒2 years after the tumor appearance. Molecular mechanisms of uveal melanoma carcinogenesis are poorly understood, and have already been shown to be different from those of skin melanoma. Activating mutations in the GNAQ and GNA11 genes, encoding the large G protein subunits Gq and G11, respectively, are found in 90% of UM patients. The main signaling cascade leading to the transformation of melanocytes of the uveal tract is the signaling pathway Gaq/PKC/MAPK, and the major regulators of this cascade are targets for the development of drugs. The development of the metastatic form of UM is most often associated with mutations in the genes BAP1, EIF1AX, GNA11, GNAQ, and SF3B1. A combination of a commercial expression test panel of 15 genes and a mutation panel of 7 genes, supplemented with data on the size of the primary tumor, has been shown to be highly effective prognostic signature in prediction the risk of metastases. The risk of metastases determines the choice of therapy and patient follow-up regimen. At the same time, no systemic therapy for the treatment of metastatic UM has been developed to date; new drugs undergoing clinical trials mostly refer to either targeted therapy aimed at inhibiting the protein products of mutant genes, or immunotherapy designed to stimulate an immune response against specific antigens. In addition to these approaches, the review also considers potential therapeutic targets of epigenetic regulation of UM development.

RNA polymerase III synthesizes a wide range of non-coding RNAs shorter than 400 nucleotides in length. These RNAs are involved in protein synthesis (tRNA, 5S rRNA, and 7SL RNA), maturation and splicing of different types of RNA (RPR, MRP RNA, and U6 snRNA), regulation of transcription (7SK RNA), replication (Y RNA), and intracellular transport (vault RNA). BC200 and BC1 RNA genes are transcribed by RNA polymerase III in neurons only where these RNAs regulate protein synthesis. Mutations in the regulatory elements of the genes transcribed by RNA polymerase III as well as in transcription factors of this RNA polymerase are associated with the development of a number of diseases, primarily oncological and neurological. In this regard, the mechanisms of regulation of the expression of the genes containing various RNA polymerase III promoters were actively studied. This review describes the structural and functional classification of polymerase III promoters, as well as the factors involved in the regulation of promoters of different types. A number of examples demonstrate the role of the described factors in the pathogenesis of human diseases.

The study investigated the effect of knockout of six Hsp70 genes (orthologues of the mammalian genes Hspa1a, Hspa1b, Hspa2 and Hspa8) on age-related changes in gene expression in the legs of Drosophila melanogaster, which contain predominantly skeletal muscle bundles. For this, the leg transcriptomic profile was examined in males of the w¹¹¹⁸ control line and the Hsp70^– line on the 7th, 23rd and 47th days of life. In w¹¹¹⁸ flies, an age-related decrease in the locomotion (climbing) speed (a marker of functional state and endurance) was accompanied by a pronounced change in the transcriptomic profile of the leg skeletal muscles, which is conservative in nature. In Hsp70^– flies, the median lifespan was shorter and the locomotion speed was significantly lower compare to the control; at the same time, complex changes in the age-related dynamics of the skeletal muscle transcriptome were observed. Mass spectrometry-based quantitative proteomic showed that 47-day-old Hsp70^– flies, compared with w¹¹¹⁸, demonstrated multidirectional changes in the content of key enzymes of glucose metabolism and fat oxidation (glycolysis, pentose phosphate pathway, Krebs cycle, beta-oxidation and oxidative phosphorylation). Such dysregulation may be associated with a compensatory increase in the expression of other genes encoding chaperones (small Hsp, Hsp40, 60, and 70), which regulate specific sets of target proteins. Taken together, our data show that knockout of six Hsp70 genes slightly reduces the median lifespan of flies, but significantly reduces the locomotion speed, which may be associated with complex changes in the transcriptome of the leg skeletal muscles and with multidirectional changes in the content of key enzymes of energy metabolism.

An inhibitor of the complement system CD55/DAF is expressed on many cell types. Dysregulation of CD55 expression is associated with increased disease severity during influenza A infection, as well as with vascular complications in pathologies involving excessive activation of the complement system. Using a luciferase reporter system, we performed functional analysis of the single nucleotide polymorphism rs2564978 located in the promoter of the CD55 gene in human pro-monocytic cell line U937. We have shown a decreased activity in activated U937 cells of the CD55 gene promoter carrying minor rs2564978(T) allele associated with the severe course of influenza A(H1N1)pdm09. Using bioinformatic resources, we determined that transcription factor PU.1 can potentially bind to the CD55 promoter region containing rs2564978 in an allele-specific manner. The involvement of PU.1 in modulating CD55 promoter activity was determined by genetic knockdown of PU.1 using small interfering RNAs under specific monocyte activation conditions.

Multiple exogenous or endogenous factors alter gene expression patterns by different mechanisms that yet are poorly understood. We used RNA-Seq analysis in order to study changes in gene expression in melanoma cells capable to vasculogenic mimicry upon action of inhibitor of vasculogenic mimicry. Here, we describe that the drug induces a strong upregulation of 50 genes controlling cell cycle and microtubule cytoskeleton coupled with a strong downregulation of 50 genes controlling different cellular metabolic processes. We found that both groups of genes are simultaneously regulated by multiple sets of transcription factors. We conclude, that one way for coordinated regulation of big groups of genes is the regulation simultaneously by multiple transcription factors.

Titin is a multidomain protein of striated and smooth muscles of vertebrates. The protein consists of repeating immunoglobulin-like (Ig) and fibronectin-like (FnIII) domains, which are β-sandwiches with a predominant β-structure, and also contains disordered regions. In this work, the methods of atomic force microscopy (AFM), X-ray diffraction and Fourier transform infrared spectroscopy were used to study the morphology and structure of aggregates of rabbit skeletal muscle titin obtained in two different solutions: 0.15 M glycine-KOH, pH 7.0 and 200 mM KCl, 10 mM imidazole, pH 7.0. According to AFM data, skeletal muscle titin formed amorphous aggregates of different morphology in the above two solutions. Amorphous aggregates of titin formed in a solution containing glycine consisted of much larger particles than aggregates of this protein formed in a solution containing KCl. The “KCl-aggregates” according to AFM data had the form of a “sponge”-like structure, while amorphous “glycine-aggregates” of titin formed “branching” structures. Spectrofluorometry revealed the ability of titin “glycine aggregates” to bind to the dye thioflavin T (TT), and X-ray diffraction revealed the presence of one of the elements of the amyloid cross β-structure, a reflection of ~4.6 Å, in these aggregates. These data indicate that the “glycine-aggregates” of titin are amyloid or amyloid-like. No similar structural features were found in titin “KCl-aggregates”; they also did not show the ability to bind to thioflavin T, indicating the non-amyloid nature of these titin aggregates. Fourier transform infrared spectroscopy revealed differences in the secondary structure of the two types of titin aggregates. The data obtained demonstrate the features of structural changes during the formation of intermolecular bonds between molecules of the giant titin protein during its aggregation. The data expand the understanding of the process of amyloid protein aggregation.