Polar Auxine Transport - Breakthrough in Research

Summary: The results of molecular dissection of aux1 and pin mutants were the breakthrough in understanding the phenomenon of auxin polar transport. The AUX1 and PIN genes were found to encode cellular influx and efflux carriers of auxin. Using immunolocalization method, a specific and polar localization of those peptides in shoot and root cells of Arabidopsis thaliana has been indicated. It has been found that the localization of PIN proteins undergoes dynamic changes involving vesicular transport and cytoskeleton. Further information of auxin polar transport was provided by auxin transport inhibitor studies – fitotropins. Though the role of auxinpolar transport in photo- and gravitropic responses is not fully established, the recent data suggest that action of photo- and gravistimuli results in asymmetric distribution of auxin that may be a consequence of the relocalisation of specific influx and efflux carriers.

Key words: auxin, auxin polar transport, fitotropins  

Beacon - Bioactive Peptide Related to Obesity

Summary: Beacon is a small protein composed of 73 amino acids, product of a recently discovered gene expressed in the hypothalamus and many others tissues. Beacon is known also as ubiquitin-like protein 5 (UBL5) and homologous to ubiquitin 1 (Hub1). Expression of beacon mRNA in the hypothalamus is positively correlated with percentage of body fat in Psammomys obesus (unique polygenic animal model of obesity and type 2 diabetes). P. obesus have elevated expression of beacon gene in hypothalamus at an early age. Hypothalamic overexpression of beacon leads to development of obesity and insulin resistance in these animals. Intracerebroventricular administration of beacon to Psammomys obesus results in a dose dependent increase in food intake, body weight and in neuropeptide Y gene expression in hypothalamus. Simultaneous treatment with beacon and NPY causes greater effect on increase of body weight than that observed after NPY only administration. Beacon-related increase in body weight is due to increased food intake, without effect on nutrient partitioning, physical activity or energy expenditure. Individuals of Psammomys obesus species with genetic predisposition for the development of obesity and type 2 diabetes have elevated hypothalamic gene expression, glucose and insulin level at 4. week after birth. The increase of body weight is observed from 8. week of postnatal development. Beacon interacts with three members of subfamily of kinases (CLKs) of cdc2/cdc28-like kinase family. This peptide binds to CLKs but it is not a substrate for phosphorylation. Mechanism of beacon action and its role remain unclear.

Key words: beacon, ubiquitin-like protein 5, homologous to ubiquitin 1, Psammomys obesus, energy balance, cdc2/cdc28-like kinases, obesity, type 2 diabetes  

Small Interfering RNA Application for Silencing of Gene Expression in Mammalian Cells

Summary: The ability to inhibit specific gene expression represents a promising idea of terapeutic strategies to control diseases such as neurodegeneration, autoimmunology disease and cancer. Theconcept of using RNA molecules as therapeutic agents is based on its crucial biochemical features. In fact, phenomena of RNAi, at first discovered in plants may be successfully employed to inhibit by siRNA expression of indicated gene in mammalian cells. Inhibition of gene expression by small interfering RNA (siRNA) is based on process of silencing gene expression that naturally occurs and is called RNA interference (RNAi). Although molecular mechanism of RNAi needs clarification, short dsRNA termed small interfering RNA seems to be essential for this pathway of gene silencing. siRNA is generated by cleavage of dsRNA (exogenous or endogenous) by RNase III like nuclease named in human cells Dicer. In the second step siRNA is incorporated into a protein complex called RNA Induced Silencing Complex (RISC). It seems to be rybonucleoprotein complex with several enzyme activities. In the end, target mRNA is recognized by siRNA and degraded. There are some approaches to achieve RNAi-based target gene silencing in mammalian cells. One of the most effective method is DNA vector-based strategy for delivering siRNAcomplementary to target mRNA. However, siRNA is double stranded molecule  with 3’ termini overhangs, hairpin RNA (hpRNA) are recognized by Dicer, degraded to siRNA and after that working in a common way. This is the reason to design of 19–21 nt hairpin RNA encoding oligonucleotides complementary to target mRNA. After cloning into vectors the hairpin RNA complementary to target mRNA will be transcribed in vivo under the control of RNA Pol III promotor. Many features of described phenomena such as substrate selectivity, is challenging to employ it as a molecular medicine instrument. At present, the major obstacle to use siRNA tools for therapies is selection of siRNA sequence because biochemical mechanism of specific gene silencing still remains unclear. Moreover, the delivery problem should be solved to introduce enough amout of siRNA into target cells in vivo.

Key words: Co-suppression, RNA interference (RNAi), Posttranscriptional Gene Silencing (PTGS), Transcriptional Gene Silencing (TGS), small interfering RNA (siRNA), RNA Induced Silencing Complex (RISC), hairpin RNA (hpRNA)
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Viral Delivery Systems in Gene Therapy and Adeno-Associated Viral (AAV) Vectors

Summary: Gene therapy has been proposed for the treatment of various diseases including cancer, AIDS, cardiovascular disfunctions. Nevertheless most of gene therapy approaches suffer from very weak efficiency of gene delivery and poor gene expression. To date, viral delivery methods are characterized by the highest transfection rates in vivo. Adeno-associated viral system is very promising new strategy in gene therapy applications for many reasons: AAV vectors seem to be safer than popular adenoviruses and retroviruses, they infect both dividing and non-dividing cells of broad host range and AAV vectors also permit stable and efficient integration of DNA into host genome. Many gene therapy experiments have used AAV delivery system with significant success. The promising outcomes have observed in vitro and in vivo studies. The results demonstrate that AAV vectors can efficiently transfer therapeutic genes to a number of different cell types – muscle, liver, neurons, cancer.

Key words:  viral vectors, gene therapy  

Ferritin Variability in Patological States

Summary: Ferritin plays very important role in all living species by storing iron in bioavailable and nontoxic form. Its synthesis is tightly regulated at transcriptional as well as translational level. Ferritin expression is influenced by several factors. Maintenance of right ferritin level is of key importance for an organism and serves as one of health indicators. Presenting latest results conserning ferritin subunits variability in case of rheumatoid arthritis and adult onset Still’s diseasepatients and subjects with upregulated ferritin biosynthesis (hereditary hyperferritinemia cataract syndrome and cancers), authors are answering a question weather there is a simple correlation between health condition and ferritin amount and weather subunit composition changes or their modiffication indicate a specific patological state.

Key words: ferritin, cancers, anemia, rheumatoid arthritis, adult onset Still’s disease, hereditary hyperferritinemia cataract syndrome  

NKG2D Receptor and its Ligands

Summary:  Effector cells of the immune system can recognize infected, transformed or as recently demonstrated, stressed cells. The recognition of the latter is based on the detection of cell surface molecules induced by cellular stress. The best known receptor for the recognition of these molecules is a C-type lectin – NKG2D expressed by NK cells, Tgd, CD8+ Tab cells, and macrophages. There are 4 families of ligands for NKG2D. Theseare human MIC A and B molecules, ULBP and murine RAE-1 and H60. Although there is little homology between these molecules, they are all classified as nonclassical MHC class I molecules. All but ULBP, the regulation of which is unknown and seems to be the most complex, are  expressed on the surface of stressed (e.g. heat or oxidative stress), infected and transformed cells. NKG2D-mediated recognition of these cells leads to co-stimulation or to the activation of the immune cells and the cytotoxic reaction towards target cells. Better understanding of the functions of stress-induced ligands for activating NKG2D receptors might potentially be exploited for new cancer immunotherapy strategies.

Key words: NKG2D, MIC, ULBP, NK  cells.

Expression of Superoxide Dismutase Genesin State of Oxidative Stress

Summary: The paper  describes superoxide dismutase (SOD) genes structure and presents latest news about their expression, with special consideration of regulation MnSOD gene expression mechanisms in the state of oxidative stress.

Key words: superoxide dismutase, oxidative stress, expression, transcription factors  

Molecular Mechanisms of Cytokinin Action

Summary: Cytokinins are plant hormones promoting cell division and differentiation. In the last decade, genetic and molecular analysis of mutants has provided valuable insights into molecular mechanisms of the action of this class of plant hormones. This presented paper focuses on the recent research results in the detecting components and the rules of perception and the function of cytokinin signal transduction pathway in plant cell. Till now, some of cytokinins binding proteins: CKI1, CRE1, AHK2/3/4 have been identified as cytokinins receptors and their genes were also described. The common feature of these receptors is the fact that proteins possess catalytic activity of histidine kinase. The proposed cytokinin signal transduction pathway is a phosphorelay pathway similar to bacterial two-component response system. The structure and function of AHP proteins, which mediate in transferring of cytokinin signal to the nucleus, was found. It was described, that genes encoding of proteins ARR so-called response regulators, act as primary responses genes, which induction generates typical plant cells reactions to cytokinins. Recent advances in the study of cell cycle indicate, that cytokinins play a central role in the regulation of cell proliferation and this mechanism bases on the induction of gene expressions encoding cyclin D3. Discovering the way of Perception and cytokinin signal transduction pathway, which occurs in the plant cell is required to understand the different effects of these phytohormones on plant biochemistry and physiology.

Keywords: cytokinins, receptors, cytokinin signal transduction pathway, primary responses genes, histidine kinase, response regulators, cyclin D3  

Perineuronal Nets - Enigmatic Structures of the Nervous System

Summary:The extracellular matrix of the nervous system is complex structural entity, that in addition to serving a structural function, also profoundly affects the cellular physiology of an organism like cell adhesion, migration, proliferation and differentiation. Perineuronal nets are aggregations of the extracellular matrix components around pericaria and proximal dendrites of some neurons. They form reticular structures consisted of glycoproteins and proteoglycans, which can be found in virtually all regions of CNS. The role of this structures still remain obscure, however it is known that they are involved in neurite growth and synaptic plasticity. They also can have neuroprotective effect in neurodegenerative diseases and inflammation processes.

Key words:  perineuronal nets, extracellular matrix, proteoglycans  

Developmental Disorders and Dysfunction of Gonads as a Result of Abnormal Action of Hormones Responsible for Male Reproductive System Development

Summary: The male reproductive system development is induced and controlled by hormones produced in the fetal gonad. The androgen receptor mutation which results in androgen insensitivity or 5a-reductase deficiency, maycause developmental disorders and frequently male infertility. Similar effects are produced in the congenital estrogen deficiency as a result of the mutation in aromatase P450 gene or the estrogen resistance syndrome connected with the mutation in the estrogen-receptor gene. Exposure in fetal and neonatal life of male animals to exogenous estrogen can result in developmentalabnormalities as a consequence of abnormal balance in action between androgens and estrogens. The increasing incidence of dysfunction and disorders of male reproductive system, and a decline of sperm counts by about half in the past 50 years, support the hypothesis that environmental hormones can induce disorders and dysfunction of the male reproductive system which can be manifested in adult life.

Key words: male reproductive system development, androgens, estrogens environmental hormones  

Polyamines in Chloroplasts

Summary: Polyamines have been found in chloroplasts of Euglena gracilis, Helianthus tuberosus, spinach and maize. By using a narrow-bore HPLC method the presence of the three main polyamines, i.e. putrescine, spermidine, spermine, in thylakoid membranes of spinach leaves was determined. These polyamines were found to be associated with the light-harvesting complex LHCII and the PSII-reaction centre of spinach.An important extension of that observation was finding that the activity of intraplastidic transglutaminase was stimulated by calcium ions and light. This enzyme catalyzed the incorporation of polyamines into thylakoid membranes and stromal proteins. For Helianthus tuberosus the apoproteins of the  chlorophyll-a/b antenna complex (LHCII, CP24, CP26, CP29) and the large subunit of ribulose – 1,5-bisphosphate carboxylase/oxygenaze was identifiedas substrates for plastidic transglutaminase.

Key words:  polyamines, chloroplasts, transglutaminases

Signal Transduction Pathways Activated by Phytochromes,the Plant Photoreceptors Perceiving Red and Far-Red Light

Summary: The phytochromes are plant cytoplasmic photoreceptors sensitive to red and far-red light that in active Pfr form migrate to the nucleus in response to light. Results of the current studies demonstrate that the phytochromes have at least two different modes of action. On one hand, they function as light-regulated kinases phosphorylating some proteins (PKS1, Aux/IAA, cryptochromes, NDPK2), on the other, they directly interact withsome nuclear proteins (PIF3, HFR1/REP/RSF1, PIF4, ELF3, ARR4) and act as transcriptional modulators. Besides, several genes involved in PhyA or PhyB downstream signal transduction pathways were identified. Encoded proteins are the both positively and negatively acting components that regulate photomorphogenesis and the circadian clock. The large subset of the encoded proteins (COP1, signalosome COP9, COP10) are components of a ubiquitin-proteasome pathway that functions in signaling by targeted degradation of transcription regulators (HY5, HYH, LAF1)

Key words:  phytochromes, signal transduction pathways, transcription regulators, mutants cop/det/fus,  signalosome COP9/CSN, E3 ligases  

Merlin - the Wizard Among Tumour Supressor Protein

Summary: Merlin is an extraordinary tumour suppressor protein. It takes part both in cell-cycle regulation as well as in the cytoskeleton formation. In the structure of merlin a FERM domain found in various protein and a-helical C-terminal fragment can be distinguished. Merlin's activity is regulated by the transitions between the open and the closed form in which FERM domain interacts with the a-helical C-terminal fragment.In the open form merlin associates with various adhesive, structural and regulatory proteins. In the closed form it associates with the CD44 protein, which probably determines its suppressory properties. The suppression mechanism involving merlin has not yet been explained. The proposed models indicate merlin's involvement both in the generation of thereversible loop of the small-GTPas's signal path as well as in the contactinhibition.

Key words:: neurofibromatosis type 2, NF2, tumour supressor..  

Physiological and Molecular Plant Responseto Dehydration Stress

Summary: Cellular dehydration is caused by abiotic factors like drought, high salinity and low temperature. Plants respond to stress with many changes at physiological and molecular level. They accumulate compatibile solutes, among them non-reducing sugars, some amino acids, organic acids, osmoprotectans and protective polypeptides. This substances prevent water efflux outside the cell by reducing its chemical potential. Metabolic adjustment to stress involves changes in number genes expression. Theyencode enzymatic polypeptides ivolved in different metabolic pathways (desaturases, glucosyl transferase, superoxide dismutase, MAP kinases), hydrophylic proteins (dehydrins, osmotins), and also regulatory elements which interact with transcriptional activators found in promoters of genes transcribed under stress conditions. It is proposed that four signal transduction pathways function under cell dehydration: two ABA-independent and two ABA-dependent. ABA-independent cascade is activated by cold whereas by drought  both of them.

Key words:  dehydration, compatible solutes, hydrofilic polypeptides, ABA-dependent and ABA-independent pathways