Vol 83, No 11 (2018)

CDKN2A is one of the most studied tumor suppressor genes. It encodes the p16-INK4a protein that plays a critical role in the cell cycle progression, differentiation, senescence, and apoptosis. Mutations in CDKN2A or dysregulation of its functional activity are frequently associated with various types of human cancer. As a cyclin-dependent kinase inhibitor, p16-INK4a forms a complex with cyclin-dependent kinases 4/6 (CDK4/6) thereby competing with cyclin D. It is believed that the helix-turn-helix structures in the content of tandem ankyrin repeats in p16-INK4a are required for the protein interaction with CDK4. Until recently, the mechanisms considered to be involved in the regulation of p16-INK4a functions and cancer development have been mutations in DNA, homozygous or heterozygous gene loss, and methylation of CDKN2A promoter region. In this review, we discuss recent findings on the regulation of p16-INK4a by covalent modifications at both transcriptional and post-translational levels.

Modern achievements in the understanding of tissue regeneration, identification of endogenous cell sources for regeneration, and development of approaches for induction and differentiation of pluripotent stem cells have open broad prospects for regenerative medicine. However, application of the obtained information in medicine is hindered by insufficient knowledge on the molecular factors and their combinations capable of regulating the age and fate of cellular sources for eye tissue reparation as well as on the regenerative responses of these cells. In the review, we present our own and literature data on cells serving as endogenous sources for eye tissue regeneration in lower and higher vertebrates and properties of gene expression that allow these cells to maintain their juvenile phenotype. Transcription factors and signal pathways providing cell juvenile status as well as cell reprogramming and entry into the S-phase are discussed. The role of systemic factors (blood and immune system factors, hormones, oxidative stress products, and cell rejuvenation factors) in these processes and their interaction with local factors of the cell environment are described. Molecular factors and conditions for induction of reprogramming and proliferation of cellular sources involved in regeneration in vitro are analyzed with special attention to the role of epigenetic factors (associated with cell senescence, in particular) in the source cells conversion during eye tissue regeneration.

The review discusses the data on vitamin D accumulation in animals, plants, and other organisms. 7-Dehydrocholesterol (7-DHC) and ergosterol are considered to be the only true precursors of vitamin D, although even vitamin D₂ (ergocalciferol) is not fully comparable to vitamin D₃ (cholecalciferol) in regard to their functions. These precursors are converted by UV radiation into the corresponding D vitamins. There are a few published reports that this reaction can also occur in the dark or under blue light, which is unexpected and requires explanation. Another unexpected result is conversion of pro-vitamins D (7-DHC and ergosterol) into vitamin D₃ and D₂ via pre-vitamin D at low temperatures (<16°C) in the lichen Cladonia rangiferina. An extensive survey of literature data leads to the conclusion that vitamin D is synthesized from (1) 7-DHC via lanosterol (D₃) in land animals; (2) 7-DHC via cycloartenol (D₃) in plants; (3) ergosterol via lanosterol (D₂) in fungi; and (4) 7-DHC or ergosterol (D₃ or D₂) in algae. Vitamin D primarily accumulates in organisms, in which it acts as a pro-hormone, e.g., land animals. It can also be found as a degradation product in many other species, in which spontaneous conversion of some membrane sterols upon UV irradiation leads to the formation of vitamins D₃ or D₂, even if they are not necessarily needed by the organism. Such products accumulate due to the absence of metabolizing enzymes, e.g., in algae, fungi, or lichens. Other organisms (e.g., zooplankton and fish) receive vitamins D with food; in this case, vitamins D do not seem to carry out biological functions; they are not metabolized but stored in cells. A few exceptions were found: the rainbow trout and at least four plant species that accumulate active hormone calcitriol (but not vitamin D) in relatively high amounts. As a result, these plants are very toxic for grazing animals (cause enzootic calcinosis). In connection with the proposal of some scientists to produce large quantities of vitamin D with the help of plants, the accumulation of calcitriol in some plants is discussed.

3-Deoxyglucosone (3DG) is a highly reactive dicarbonyl species, and its accumulation evokes carbonyl and oxidative stress. Our recent data reveal the role of 3DG as an independent factor for the development of prediabetes and suggest that intestine could be its novel target tissue. The present study investigated whether exogenous 3DG increases intestinal permeability by triggering carbonyl and oxidative stress, thus contributing to β-cell dysfunction. Rats were administered 3DG for two weeks by gastric gavage. Then levels of insulin, ROS, MDA, SOD, NLRP3, TNF-α and IL-1β in blood plasma as well as the ROS level and content of TNF-α and IL-1β in pancreas were assessed. Also, the expression of E-cadherin and ZO-1 as well as levels of 3DG, protein carbonylation, ROS, TNF-α and IL-1β in colon were determined. The 3DG-treated rats showed an elevation in systemic oxidative stress (ROS, MDA and SOD) and in inflammation (TNF-α and IL-1β), decreased plasma insulin level 15 min after the glucose load, and increased levels of TNF-α, IL-1β and ROS in pancreatic tissue. In colon tissues of the 3DG-treated rats, decreased E-cadherin expression and increased ROS production as well as an elevation of TNF-α and IL-1β levels were observed. Interestingly, elevation of colon protein carbonylation was observed in the 3DG-treated rats that displayed 3DG deposition in colon tissues. We revealed for the first time that 3DG deposition in colon triggers carbonyl and oxidative stress and, as a consequence, impairs gut permeability. The enhanced intestinal permeability caused by 3DG deposition in colon results in systemic and pancreatic oxidative stress and inflammatory process, contributing to the development of β-cell dysfunction.

Lymphocyte phosphatase-associated phosphoprotein (LPAP) is a molecular partner of CD45 phosphatase that plays a key role in the regulation of antigen-specific activation of lymphocytes. The functions of LPAP still remain unknown. We believe that studying LPAP phosphorylation pathways could shed light on its functions. In this work, we studied the phosphorylation of LPAP ectopically expressed in non-lymphoid cells in order to determine the effect of LPAP interaction partners on its phosphorylation. We found that phosphorylation at Ser153 and Ser163 in non-hematopoietic HEK293 cells was conserved, while phosphorylation at Ser99 and Ser172 was almost absent. The pattern of LPAP phosphorylation in K562 erythroid and U937 myeloid cells expressing endogenous CD45 protein was similar to that observed in T and B lymphocytes. We demonstrated for the first time that LPAP is a substrate for protein kinase CK2 that phosphorylates it at Ser153, presumably ensuring LPAP resistance to degradation.

Complete enzymatic degradation of plant polysaccharides is a result of combined action of various carbohydrate-active enzymes (CAZymes). In this paper, we demonstrate the potential of the filamentous fungus Scytalidium candidum 3C for processing of plant biomass. Structural annotation of the improved assembly of S. candidum 3C genome and functional annotation of CAZymes revealed putative gene sequences encoding such proteins. A total of 190 CAZyme-encoding genes were identified, including 104 glycoside hydrolases, 52 glycosyltransferases, 28 oxidative enzymes, and 6 carbohydrate esterases. In addition, 14 carbohydrate-binding modules were found. Glycoside hydrolases secreted during the growth of S. candidum 3C in three media were analyzed with a variety of substrates. Mass spectrometry analysis of the fungal culture liquid revealed the presence of peptides identical to 36 glycoside hydrolases, three proteins without known enzymatic function belonging to the same group of families, and 11 oxidative enzymes. The activity of endohemicellulases was determined using specially synthesized substrates in which the glycosidic bond between monosaccharide residues was replaced by a thiolinkage. During analysis of the CAZyme profile of S. candidum 3C, four β-xylanases from the GH10 family and two β-glucanases from the GH7 and GH55 families were detected, partially purified, and identified.

In this paper, we present the new Cysmotif searcher pipeline for identification of various antimicrobial peptides (AMPs), the most important components of innate immunity, in plant transcriptomes. Cysmotif searcher reveals and classifies short cysteine-rich amino acid sequences containing an open reading frame and a signal peptide cleavage site. Due to the combination of various search methods, Cysmotif searcher allows to obtain the most complete repertoire of AMPs for one or more transcriptomes in a short amount of time. The pipeline performance is estimated on the model plant Arabidopsis thaliana and nine other plants, including cultivated and wild species. The obtained results are compared to the existing annotation (A. thaliana) and results of conventional homology search (other plants). The comparison is carried out for known families of plant AMPs and newly discovered peptides that could not be assigned to existing families. The applicability of Cysmotif searcher in detecting new AMPs is discussed, and some practical recommendations on the pipeline usage for end users are given. The Cysmotif searcher pipeline is free for academic use and can be downloaded from Github (https://doi.org/github.com/fallandar/cysmotifsearcher).

Errors have been found in polysaccharide structures on pages 603 (Fig. 3), 606 (Figs. 13-15) and 607 (Fig. 17). The following are the correct structures.