Saccharomyces cerevisiae as a model system to study the response to anticancer agents

The Promising Role of Selenium and Yeast in the Fight Against Protein Amyloidosis

In recent years, increasing attention has been paid to research on diseases related to the deposition of misfolded proteins (amyloids) in various organs. Moreover, modern scientists emphasise the importance of selenium as a bioelement necessary for the proper functioning of living organisms. The inorganic form of selenium-sodium selenite (redox-active)-can prevent the formation of an insoluble polymer in proteins. It is very important to undertake tasks aimed at understanding the mechanisms of action of this element in inhibiting the formation of various types of amyloid. Furthermore, yeast cells play an important role in this matter as a eukaryotic model organism, which is intensively used in molecular research on protein amyloidosis. Due to the lack of appropriate treatment in the general population, the problem of amyloidosis remains unsolved. This extracellular accumulation of amyloid is one of the main factors responsible for the occurrence of Alzheimer's disease. The review presented here contains scientific information discussing a brief description of the possibility of amyloid formation in cells and the use of selenium as a factor preventing the formation of these protein aggregates. Recent studies have shown that the yeast model can be successfully used as a eukaryotic organism in biotechnological research aimed at understanding the essence of the entire amyloidosis process. Understanding the mechanisms that regulate the reaction of yeast to selenium and the phenomenon of amyloidosis is important in the aetiology and pathogenesis of various disease states. Therefore, it is imperative to conduct further research and analysis aimed at explaining and confirming the role of selenium in the processes of protein misfolding disorders. The rest of the article discusses the characteristics of food protein amyloidosis and their use in the food industry. During such tests, their toxicity is checked because not all food proteins can produce amyloid that is toxic to cells. It should also be noted that a moderate diet is beneficial for the corresponding disease relief caused by amyloidosis.

Application of microscopy and spectroscopy in investigating anti-cancer potential of Achyranthes aspera L. leaves

The genus Achyranthes belong to the family Amaranthaceae which constitutes an important group of herbs and shrubs with immense medicinal value. The present research work was conducted to investigate the anticancer potential of Achyranthes aspera L. leaves by focusing on the antioxidant, aniproliferative and antimitotic activities of leaf extracts. Plant extraction was carried out by soxhelt method with different solvents. Phytochemical characterization of the plants extracts using chemical methods identified the presence of cardiac glycosides, saponins, coumarins, proteins, tannins, flavonoids and triterpenes. Alkaloid was present in methanolic and ethanolic extract. High performance liquid chromatography showed presence of different concentration of myricetin, quercetin and kaempferol in different extracts with the highest concentration of myricetin (84.53 μg/mL) in n-butanolic extract. The extracts were then tested for antioxidant activity using 2,2-diphenylpicrylhydrazyl (DPPH) radical scavenging assay by spectrophotometric method. In DPPH radical scavenging assay, antioxidant activity of A. aspera ranged between 79.78 ± 0.034% and 58.63 ± 0.069%. Highest antioxidant activity was observed for methanolic extract and lowest for acetone. Antimitotic activity was determined by using Allium cepa assay in which microscopic investigation was carried out to observe normal and abnormal phases of mitosis. In this assay, n-butanolic extract had highest antimitotic activity with minimum mitotic index at 2 mg/mL (57 ± 0.0351%). The plant extracts also caused chromosomal and mitotic aberrations which were clearly observed under 40× and 100× magnification of compound microscope. Antiproliferative activity was determined by using yeast cell model in which light microscope with hemocytometer was used for cell counting. In case of Antiproliferative activity, the ethyl acetate extract of A. aspera had highest antiproliferative activity with lowest cell viability (22.14 ± 0.076%) at highest extract concentration (2 mg/mL) while methanol extract of A. aspera had highest antiproliferative activity with lower cell viability (24.24 ± 0.057%) at lowest extract concentration (0.25 mg/mL). The results of the study indicated that the leaves extract of A. aspera have strong potential to be used as a source of anti-cancer agent. RESEARCH HIGHLIGHTS: Achyranthes aspera L. leaves have various phytochemicals which contribute to its medicinal properties Various extracts of the leaves of A. aspera L. possess antioxidant, antimitotic and antiproliferative potential The results of the study indicated that the leaves extract of A. aspera have strong potential to be used as a source of anti-cancer agent.

A PKC that controls polyphosphate levels, pinocytosis and exocytosis, regulates stationary phase onset in Dictyostelium

Many cells can pause their growth cycle, a topic much enriched by studies of the stationary phase (SP) of model microorganisms. While several kinases are implicated in SP onset, a possible role for protein kinase C remains unknown. We show that Dictyostelium discoideum cells lacking pkcA entered SP at a reduced cell density, but only in shaking conditions. Precocious SP entry occurs because extracellular polyphosphate (polyP) levels reach a threshold at the lower cell density; adding exopolyphosphatase to pkcA- cells reverses the effect and mimics wild type growth. PkcA's regulation of polyP depended on inositol hexakisphosphate kinase and phospholipase D. PkcA- mutants also had higher actin levels, higher rates of exocytosis and lower pinocytosis rates. Postlysosomes were smaller and present in fewer pkcA- cells, compared to the wildtype. Overall, the results suggest that a reduced PkcA level triggers SP primarily because cells do not acquire or retain nutrients as efficiently, thus mimicking, or amplifying, the conditions of actual starvation.

Yeast Rpn4 Links the Proteasome and DNA Repair via RAD52 Regulation

Environmental and intracellular factors often damage DNA, but multiple DNA repair pathways maintain genome integrity. In yeast, the 26S proteasome and its transcriptional regulator and substrate Rpn4 are involved in DNA damage resistance. Paradoxically, while proteasome dysfunction may induce hyper-resistance to DNA-damaging agents, Rpn4 malfunction sensitizes yeasts to these agents. Previously, we proposed that proteasome inhibition causes Rpn4 stabilization followed by the upregulation of Rpn4-dependent DNA repair genes and pathways. Here, we aimed to elucidate the key Rpn4 targets responsible for DNA damage hyper-resistance in proteasome mutants. We impaired the Rpn4-mediated regulation of candidate genes using the CRISPR/Cas9 system and tested the sensitivity of mutant strains to 4-NQO, MMS and zeocin. We found that the separate or simultaneous deregulation of 19S or 20S proteasome subcomplexes induced MAG1, DDI1, RAD23 and RAD52 in an Rpn4-dependent manner. Deregulation of RAD23, DDI1 and RAD52 sensitized yeast to DNA damage. Genetic, epigenetic or dihydrocoumarin-mediated RAD52 repression restored the sensitivity of the proteasome mutants to DNA damage. Our results suggest that the Rpn4-mediated overexpression of DNA repair genes, especially RAD52, defines the DNA damage hyper-resistant phenotype of proteasome mutants. The developed yeast model is useful for characterizing drugs that reverse the DNA damage hyper-resistance phenotypes of cancers.

Cytotoxicity of Oleandrin Is Mediated by Calcium Influx and by Increased Manganese Uptake in Saccharomyces cerevisiae Cells

Oleandrin, the main component of Nerium oleander L. extracts, is a cardiotoxic glycoside with multiple pharmacological implications, having potential anti-tumoral and antiviral characteristics. Although it is accepted that the main mechanism of oleandrin action is the inhibition of Na⁺/K⁺-ATPases and subsequent increase in cell calcium, many aspects which determine oleandrin cytotoxicity remain elusive. In this study, we used the model Saccharomyces cerevisiae to unravel new elements accounting for oleandrin toxicity. Using cells expressing the Ca²⁺-sensitive photoprotein aequorin, we found that oleandrin exposure resulted in Ca²⁺ influx into the cytosol and that failing to pump Ca²⁺ from the cytosol to the vacuole increased oleandrin toxicity. We also found that oleandrin exposure induced Mn²⁺ accumulation by yeast cells via the plasma membrane Smf1 and that mutants with defects in Mn²⁺ homeostasis are oleandrin-hypersensitive. Our data suggest that combining oleandrin with agents which alter Ca²⁺ or Mn²⁺ uptake may be a way of controlling oleandrin toxicity.

Saccharomyces cerevisiae and Caffeine Implications on the Eukaryotic Cell

Caffeine-a methylxanthine analogue of the purine bases adenine and guanine-is by far the most consumed neuro-stimulant, being the active principle of widely consumed beverages such as coffee, tea, hot chocolate, and cola. While the best-known action of caffeine is to prevent sleepiness by blocking the adenosine receptors, caffeine exerts a pleiotropic effect on cells, which lead to the activation or inhibition of various cell integrity pathways. The aim of this review is to present the main studies set to investigate the effects of caffeine on cells using the model eukaryotic microorganism Saccharomyces cerevisiae, highlighting the caffeine synergy with external cell stressors, such as irradiation or exposure to various chemical hazards, including cigarette smoke or chemical carcinogens. The review also focuses on the importance of caffeine-related yeast phenotypes used to resolve molecular mechanisms involved in cell signaling through conserved pathways, such as target of rapamycin (TOR) signaling, Pkc1-Mpk1 mitogen activated protein kinase (MAPK) cascade, or Ras/cAMP protein kinase A (PKA) pathway.

Combined in silico and 19F NMR analysis of 5-fluorouracil metabolism in yeast at low ATP conditions

The cytotoxic effect of 5-fluorouracil (5-FU) on yeast cells is thought to be mainly via a misincorporation of fluoropyrimidines into both RNA and DNA, not only DNA damage via inhibition of thymidylate synthase (TYMS) by fluorodeoxyuridine monophosphate (FdUMP). However, some studies on Saccharomyces cerevisiae show a drastic decrease in ATP concentration under oxidative stress, together with a decrease in concentration of other tri- and diphosphates. This raises a question if hydrolysis of 5-fluoro-2-deoxyuridine diphosphate (FdUDP) under oxidative stress could not lead to the presence of FdUMP and the activation of so-called 'thymine-less death' route. We attempted to answer this question with in silico modeling of 5-FU metabolic pathways, based on new experimental results, where the stages of intracellular metabolism of 5-FU in Saccharomyces cerevisiae were tracked by a combination of 19F and 31P NMR spectroscopic study. We have identified 5-FU, its nucleosides and nucleotides, and subsequent di- and/or triphosphates. Additionally, another wide 19F signal, assigned to fluorinated unstructured short RNA, has been also identified in the spectra. The concentration of individual metabolites was found to vary substantially within hours, however, the initial steady-state was preserved only for an hour, until the ATP concentration dropped by a half, which was monitored independently via 31P NMR spectra. After that, the catabolic process leading from triphosphates through monophosphates and nucleosides back to 5-FU was observed. These results imply careful design and interpretation of studies in 5-FU metabolism in yeast.

DNA susceptibility of Saccharomyces cerevisiae to Zeocin depends on the growth phase

The aim of this study was to evaluate the level of Zeocin-induced double-strand breaks (DSBs) in Saccharomyces cerevisiae cells in a different growth phase, using constant-field gel electrophoresis (CFGE). Saccharomyces cerevisiae diploid strain D7ts1 with enhanced cellular permeability was used. The effects of growth phase and treatment time were evaluated based on Zeocin-induced DSBs, measured by CFGE. Survival assay was also applied. No protoplast isolation was necessary for the detection of DSBs in strain D7ts1. Differences in the response of cells depending on the growth phase were obtained. Cells in exponential growth phase had increased DSB levels only after Zeocin treatment with concentrations equal or higher than 200 μgml^-1. Increasing treatment time did not result in higher DSB levels. Oppositely, treatment of cells at the beginning of stationary phase with Zeocin concentrations resulted in more than 1.5-fold increase in DSB levels in comparison with those in untreated cells. Increased DSB levels were measured for all the treatment times. A dose-dependent decrease in cell survival was observed after Zeocin treatment with concentrations in the range of lethality LD₂₀-LD₅₀. A strong negative correlation was calculated between the levels of DSBs and cell survival. New information is provided concerning DNA susceptibility depending on the growth phase. DNA susceptibility is higher in cells at the beginning of stationary phase than those in exponential phase. Data presented here illustrate that the optimized by us CFGE protocol is sensitive and could be used successfully for DSB measurement in Saccharomyces cerevisiae strains with enhanced cellular permeability.

Yeast Systems Biology: The Continuing Challenge of Eukaryotic Complexity

Research on yeast has produced a plethora of tools and resources that have been central to the progress of systems biology. This chapter reviews these resources, explains the innovations that have been made since the first edition of this book, and introduces the constituent chapters of the current edition. The value of these resources not only in building and testing models of the functional networks of the yeast cell, but also in providing a foundation for network studies on the molecular basis of complex human diseases is considered. The gaps in this vast compendium of data, including enzyme kinetic characteristics, biomass composition, transport processes, and cell-cell interactions are discussed, as are the interactions between yeast cells and those of other species. The relevance of these studies to both traditional and advanced biotechnologies and to human medicine is considered, and the opportunities and challenges in using unicellular yeasts to model the systems of multicellular organisms are presented.

Interrogation of ethnomedicinal plants for synthetic lethality effects in combination with deficiency in the DNA repair endonuclease RAD1 using a yeast cell-based assay

ETHNOPHARMACOLOGICAL RELEVANCE

Plant materials used in this study were selected based on the ethnobotanical literature. Plants have either been utilized by Thai practitioners as alternative treatments for cancer or identified to exhibit anti-cancer properties.

AIM OF THE STUDY

To screen ethnomedicinal plants using a yeast cell-based assay for synthetic lethal interactions with cells deleted for RAD1, the yeast homologue of human ERCC4 (XPF) MATERIALS AND METHODS: Ethanolic extracts from thirty-two species of medicinal plants utilized in Thai traditional medicine were screened for synthetic lethal/sick interactions using a yeast cell-based assay. Cell growth was compared between the parental strain and rad1∆ yeast following exposure to select for specific toxicity of plant extracts. Candidate extracts were further examined for the mode of action using genetic and biochemical approaches.

RESULTS

Screening a library of ethanolic extracts from medicinal plants identified Bacopa monnieri and Colubrina asiatica as having synthetic lethal effects in the rad1∆ cells but not the parental strain. Synthetic lethal effects for B. monneiri extracts were more apparent and this plant was examined further. Genetic analysis indicates that pro-oxidant activities and defective excision repair pathways do not significantly contribute to enhanced sensitivity to B. monneiri extracts. Exposure to B. monneiri extracts resulted in nuclear fragmentation and elevated levels of ethidium bromide staining in rad1∆ yeast suggesting promotion of an apoptosis-like event. Growth inhibition also observed in the human Caco-2 cell line suggesting the effects of B. monnieri extracts on both yeast and human cells may be similar.

CONCLUSIONS

B. monneiri extracts may have utility in treatment of colorectal cancers that exhibit deficiency in ERCC4 (XPF).

Sensitivity of Yeast Mutants Deficient in Mitochondrial or Vacuolar ABC Transporters to Pathogenesis-Related Protein TcPR-10 of Theobroma cacao

Pathogenesis-related proteins (PRs) are induced in plants after infection by pathogens and/or abiotic stress. Among these proteins, the family 10 (PR-10) influences the biosynthesis of secondary metabolites and shows antimicrobial ribonuclease activity. TcPR-10p (Pathogenesis-related Protein 10 of Theobroma cacao) was isolated from resistant and susceptible Moniliophthora perniciosa cacao cultivars. Cell survival with Saccharomyces cerevisiae mutant lines deficient in ATP-binding cassette (ABC) transporter proteins indicated the influence on resistance to TcPR-10p. Proteins of the ABC transport type are considered important in the process of resistance to antimicrobials and toxins. Thus, the objective of this work was to observe the sensitivity of ABC transporter yeast mutants in the presence of the TcPR-10p. Chronic exposure of S. cerevisiae mitochondrial (BYatm1Δ and BYmdl1Δ) and vacuole (BYnft1Δ, BYvmr1Δ, BYybt1Δ, BYycf1Δ and BYbpt1Δ) ABC transporter mutants to TcPR-10p (3 μg/mL, 0, 6, 12 and 24 h) was performed. Two TcPR-10p sensitive strains (BYmdl1Δ and BYnft1Δ) were submitted to a fluorescence test with the fluorogenic dihydroethidium (DHE), to visualize the presence of oxidative stress in the cells. Oxidative stress-increased sensitivity was confirmed by flow cytometry indicating induced cell death either via apoptosis or necrosis. This yeast data combined with previous data of literature (of M. perniciosa sensitivity to TcPR-10p) show that increased sensitivity to TcPR-10p in these mutants could be due to the TcPR10p-generated higher levels of intracellular reactive oxygen species (ROS), leading to increased cell death either via necrosis or apoptosis.

The Yeast Saccharomyces cerevisiae as a Model for Understanding RAS Proteins and their Role in Human Tumorigenesis

The exploitation of the yeast Saccharomyces cerevisiae as a biological model for the investigation of complex molecular processes conserved in multicellular organisms, such as humans, has allowed fundamental biological discoveries. When comparing yeast and human proteins, it is clear that both amino acid sequences and protein functions are often very well conserved. One example of the high degree of conservation between human and yeast proteins is highlighted by the members of the RAS family. Indeed, the study of the signaling pathways regulated by RAS in yeast cells led to the discovery of properties that were often found interchangeable with RAS proto-oncogenes in human pathways, and vice versa. In this work, we performed an updated critical literature review on human and yeast RAS pathways, specifically highlighting the similarities and differences between them. Moreover, we emphasized the contribution of studying yeast RAS pathways for the understanding of human RAS and how this model organism can contribute to unveil the roles of RAS oncoproteins in the regulation of mechanisms important in the tumorigenic process, like autophagy.

How yeast coordinates metabolism, growth and division

All cells, especially single cell organisms, need to adapt their metabolism, growth and division coordinately to the available nutrients. This coordination is mediated by extensive cross-talk between nutrient signaling, metabolism, growth, and the cell division cycle, which is only gradually being uncovered: Nutrient signaling not only controls entry into the cell cycle at the G1/S transition, but all phases of the cell cycle. Metabolites are even sensed directly by cell cycle regulators to prevent cell cycle progression in absence of sufficient metabolic fluxes. In turn, cell cycle regulators such as the cyclin-dependent kinase directly control metabolic fluxes during cell cycle progression. In this review, I highlight some recent advances in our understanding of how metabolism and the cell division cycle are coordinated in the model organism Saccharomyces cerevisiae.

The Use of Baker's Yeast in the Resazurin Reduction Test: A Simple, Low-Cost Method for Determining Cell Viability in Proliferation and Cytotoxicity Assays

Cell viability assays require expensive commercial testing kits and sophisticated cell culture techniques. Thus, a laboratory activity for testing the cellular proliferative and cytotoxic effects of certain substances using baker’s yeast (Saccharomyces cerevisiae) in resazurin reduction test (RRT) was developed. This activity is based on the fact that a laboratory-prepared resazurin has identical effects to a resazurin-based commercial kits and that S. cerevisiae is an established model system for eukaryotic organisms. Here, a complete procedure based on optimized conditions was described in detail, from preparation of test materials and solutions up to the gathering and analysis of data. This laboratory activity provides a simple and cheap alternative to conventional cell viability assays and is therefore recommended for use in institutions with limited budget for the acquisition of materials for instruction purposes.

Synthetic lethality: emerging targets and opportunities in melanoma

Great progress has been made in the treatment of melanoma through use of targeted therapies and immunotherapy. One approach that has not been fully explored is synthetic lethality, which exploits somatically acquired changes, usually driver mutations, to specifically kill tumour cells. We outline the various approaches that may be applied to identify synthetic lethal interactions and define how these interactions may drive drug discovery efforts.

Unraveling new functions of superoxide dismutase using yeast model system: Beyond its conventional role in superoxide radical scavenging

To deal with chemically reactive oxygen molecules constantly threatening aerobic life, cells are readily equipped with elaborate biological antioxidant systems. Superoxide dismutase is a metalloenzyme catalytically eliminating superoxide radical as a first-line defense mechanism against oxidative stress. Multiple different SOD isoforms have been developed throughout evolution to play distinct roles in separate subcellular compartments. SOD is not essential for viability of most aerobic organisms and intriguingly found even in strictly anaerobic bacteria. Sod1 has recently been known to play important roles as a nuclear transcription factor, an RNA binding protein, a synthetic lethal interactor, and a signal modulator in glucose metabolism, most of which are independent of its canonical function as an antioxidant enzyme. In this review, recent advances in understanding the unconventional role of Sod1 are highlighted and discussed with an emphasis on its genetic crosstalk with DNA damage repair/checkpoint pathways. The budding yeast Saccharomyces cerevisiae has been successfully used as an efficient tool and a model organism to investigate a number of novel functions of Sod1.

Screening the yeast genome for energetic metabolism pathways involved in a phenotypic response to the anti-cancer agent 3-bromopyruvate

In this study the detailed characteristic of the anti-cancer agent 3-bromopyruvate (3-BP) activity in the yeast Saccharomyces cerevisiae model is described, with the emphasis on its influence on energetic metabolism of the cell. It shows that 3-BP toxicity in yeast is strain-dependent and influenced by the glucose-repression system. Its toxic effect is mainly due to the rapid depletion of intracellular ATP. Moreover, lack of the Whi2p phosphatase results in strongly increased sensitivity of yeast cells to 3-BP, possibly due to the non-functional system of mitophagy of damaged mitochondria through the Ras-cAMP-PKA pathway. Single deletions of genes encoding glycolytic enzymes, the TCA cycle enzymes and mitochondrial carriers result in multiple effects after 3-BP treatment. However, it can be concluded that activity of the pentose phosphate pathway is necessary to prevent the toxicity of 3-BP, probably due to the fact that large amounts of NADPH are produced by this pathway, ensuring the reducing force needed for glutathione reduction, crucial to cope with the oxidative stress. Moreover, single deletions of genes encoding the TCA cycle enzymes and mitochondrial carriers generally cause sensitivity to 3-BP, while totally inactive mitochondrial respiration in the rho⁰ mutant resulted in increased resistance to 3-BP.

Reactive oxygen species and Ca2+ are involved in cadmium-induced cell killing in yeast cells

Cadmium (Cd) is one of the most toxic heavy metals. It is of great environmental concern and its toxicity has been investigated in a variety of cells. In this study, we elucidated the toxic effects of Cd in cells of yeast (Saccharomyces cerevisiae). Our results showed that Cd²⁺ (0.05-5.0 mmol·L^-1) significantly inhibited yeast cell growth, and the inhibitory effect was positively correlated with Cd²⁺ concentrations. Cd²⁺ caused loss of yeast cell viability in a concentration- and duration-dependent manner. Intracellular reactive oxygen species (ROS) and Ca²⁺ levels increased in yeast cells after exposure to 5.0 mmol·L^-1 Cd for 6 h. Cd²⁺-caused cell viability loss was blocked by antioxidants (0.5 mmol·L^-1 ascorbic acid or 500 U·mL^-1 catalase) or Ca²⁺ antagonists (0.5 mmol·L^-1 ethylene glycol tetraacetic acid or 0.5 mmol·L^-1 LaCl₃). Moreover, a collapse of mitochondrial membrane potential (ΔΨ_m) was observed in Cd²⁺-treated yeast cells. These results indicate that Cd-induced yeast cell killing was associated with the elevation of intracellular ROS and Ca²⁺ levels and also the loss of ΔΨ_m.

The Chromone Alkaloid, Rohitukine, Affords Anti-Cancer Activity via Modulating Apoptosis Pathways in A549 Cell Line and Yeast Mitogen Activated Protein Kinase (MAPK) Pathway

The field of cancer research and treatment has made significant progress, yet we are far from having completely safe, efficient and specific therapies that target cancer cells and spare the healthy tissues. Natural compounds may reduce the problems related to cancer treatment. Currently, many plant products are being used to treat cancer. In this study, Rohitukine, a natural occurring chromone alkaloid extracted from Dysoxylum binectariferum, was investigated for cytotoxic properties against budding yeast as well as against lung cancer (A549) cells. We endeavored to specifically study Rohitukine in S. cerevisiae in the context of MAPK pathways as yeast probably represents the experimental model where the organization and regulation of MAPK pathways are best understood. MAPK are evolutionarily conserved protein kinases that transfer extracellular signals to the machinery controlling essential cellular processes like growth, migration, differentiation, cell division and apoptosis. We aimed at carrying out hypothesis driven studies towards targeting the important network of cellular communication, a critical process that gets awry in cancer. Employing mutant strains of genetic model system Saccharomyces cerevisiae. S. cerevisiae encodes five MAPKs involved in control of distinct cellular responses such as growth, differentiation, migration and apoptosis. Our study involves gene knockouts of Slt2 and Hog1 which are functional homologs of human ERK5 and mammalian p38 MAPK, respectively. We performed cytotoxicity assay to evaluate the effect of Rohitukine on cell viability and also determined the effects of drug on generation of reactive oxygen species, induction of apoptosis and expression of Slt2 and Hog1 gene at mRNA level in the presence of drug. The results of this study show a differential effect in the activity of drug between the WT, Slt2 and Hog1 gene deletion strain indicating involvement of MAPK pathway. Further, we investigated Rohitukine induced cytotoxic effects in lung cancer cells and stimulated the productions of ROS after exposure for 24 hrs. Results from western blotting suggest that Rohitukine triggered apoptosis in A549 cell line through upregulation of p53, caspase9 and down regulation of Bcl-2 protein. The scope of this study is to understand the mechanism of anticancer activity of Rohitukine to increase the repertoire of anticancer drugs, so that problem created by emergence of resistance towards standard anticancer compounds can be alleviated.

Human Thyroid Cancer-1 (TC-1) is a vertebrate specific oncogenic protein that protects against copper and pro-apoptotic genes in yeast

The human Thyroid Cancer-1 (hTC-1) protein, also known as C8orf4 was initially identified as a gene that was up-regulated in human thyroid cancer. Here we show that hTC-1 is a peptide that prevents the effects of over-expressing Bax in yeast. Analysis of the 106 residues of hTC-1 in available protein databases revealed direct orthologues in jawed-vertebrates, including mammals, frogs, fish and sharks. No TC-1 orthologue was detected in lower organisms, including yeast. Here we show that TC-1 is a general pro-survival peptide since it prevents the growth- and cell death-inducing effects of copper in yeast. Human TC-1 also prevented the deleterious effects that occur due to the over-expression of a number of key pro-apoptotic peptides, including YCA1, YBH3, NUC1, and AIF1. Even though the protective effects were more pronounced with the over-expression of YBH3 and YCA1, hTC-1 could still protect yeast mutants lacking YBH3 and YCA1 from the effects of copper sulfate. This suggests that the protective effects of TC-1 are not limited to specific pathways or processes. Taken together, our results indicate that hTC-1 is a pro-survival protein that retains its function when heterologously expressed in yeast. Thus yeast is a useful model to characterize the potential roles in cell death and survival of cancer related genes.

Transcriptional remodeling in response to transfer upon carbon-limited or metformin-supplemented media in S. cerevisiae and its effect on chronological life span

One of the factors affecting chronological life span (CLS) in budding yeast is nutrient, especially carbon limitation. Aside from metabolites in the growth medium such as glucose, amino acids, and acetic acid, many pharmaceuticals have also been proven to alter CLS. Besides their impact on life span, these drugs are also prospective chemicals to treat the age-associated diseases, so the identification of their action mechanism and their potential side effects is of crucial importance. In this study, the effects of caloric restriction and metformin, a dietary mimetic pharmaceutical, on yeast CLS are compared. Saccharomyces cerevisiae cells grown in synthetic dextrose complete (SDC) up to mid-exponential phase were either treated with metformin or were subjected to glucose limitation. The impacts of these perturbations were analyzed via transcriptomics, and the common (stimulation of glucose uptake, induction of mitochondrial maintenance, and reduction of protein translation) and divergent (stimulation of aerobic respiration and reprogramming of respiratory electron transport chain (ETC)) cellular responses specific to each treatment were determined. These results revealed that both glucose limitation and metformin treatment stimulate CLS extension and involve the mitochondrial function, probably by creating an efficient mitochondria-to-nucleus signaling of either aerobic respiration or ETC signaling stimulation, respectively.

Antifungal compounds produced by Colletotrichum gloeosporioides, an endophytic fungus from Michelia champaca

In this study, eight endophytic fungi were isolated from the leaves, stems and roots of Michelia champaca. The isolates were screened and evaluated for their antifungal, anticancer and acetylcholinesterase (AChE) inhibitory activities. All of the extracts exhibited potent activity against two evaluated phytopathogenic fungi. Chemical investigation of EtOAc extracts of the endophytic fungus Colletotrichum gloeosporioides resulted in the isolation of one new compound, 2-phenylethyl 1H-indol-3-yl-acetate (1), and seven known compounds: uracil (2), cyclo-(S*-Pro-S*-Tyr) (3), cyclo-(S*-Pro-S*-Val) (4), 2(2-aminophenyl)acetic acid (5), 2(4-hydroxyphenyl)acetic acid (6), 4-hydroxy- benzamide (7) and 2(2-hydroxyphenyl)acetic acid (8). All of the compound structures were elucidated using 1D and 2D NMR and MS analyses. The antifungal and AChE inhibitory activities of compounds 1–8 were evaluated in vitro. Compound 1 exhibited promising activity against Cladosporium cladosporioides and C. sphaerospermum that was comparable to that of the positive control nystatin.

To divide or not to divide: a key role of Rim15 in calorie-restricted yeast cultures

The PAS kinase Rim15 is proposed to integrate signals from different nutrient-sensing pathways and to control transcriptional reprogramming of Saccharomyces cerevisiae upon nutrient depletion. Despite this proposed role, previous transcriptome analyses of rim15 mutants solely focused on growing cultures. In the present work, retentostat cultivation enabled analysis of the role of Rim15 under severely calorie-restricted, virtually non-growing conditions. Under these conditions, deletion of RIM15 affected transcription of over 10-fold more genes than in growing cultures. Transcriptional responses, metabolic rates and cellular morphology indicated a key role of Rim15 in controlled cell-cycle arrest upon nutrient depletion. Moreover, deletion of rim15 reduced heat-shock tolerance in non-growing, but not in growing cultures. The failure of rim15 cells to adapt to calorie restriction by entering a robust post-mitotic state resembles cancer cell physiology and shows that retentostat cultivation of yeast strains can provide relevant models for healthy post-mitotic and transformed human cells.

Classic "broken cell" techniques and newer live cell methods for cell cycle assessment

Many common, important diseases are either caused or exacerbated by hyperactivation (e.g., cancer) or inactivation (e.g., heart failure) of the cell division cycle. A better understanding of the cell cycle is critical for interpreting numerous types of physiological changes in cells. Moreover, new insights into how to control it will facilitate new therapeutics for a variety of diseases and new avenues in regenerative medicine. The progression of cells through the four main phases of their division cycle [G(0)/G(1), S (DNA synthesis), G(2), and M (mitosis)] is a highly conserved process orchestrated by several pathways (e.g., transcription, phosphorylation, nuclear import/export, and protein ubiquitination) that coordinate a core cell cycle pathway. This core pathway can also receive inputs that are cell type and cell niche dependent. "Broken cell" methods (e.g., use of labeled nucleotide analogs) to assess for cell cycle activity have revealed important insights regarding the cell cycle but lack the ability to assess living cells in real time (longitudinal studies) and with single-cell resolution. Moreover, such methods often require cell synchronization, which can perturb the pathway under study. Live cell cycle sensors can be used at single-cell resolution in living cells, intact tissue, and whole animals. Use of these more recently available sensors has the potential to reveal physiologically relevant insights regarding the normal and perturbed cell division cycle.