Yeast as a model system to screen purine derivatives against human CDK1 and CDK2 kinases

[Budding yeast, a model and a tool… also for biomedical research]

Yeast has been used for thousands of years as a leavening agent and for alcoholic fermentation, but it is only in 1857 that Louis Pasteur described the microorganism at the basis of these two tremendously important economic activities. From there, yeast strains could be selected and modified on a rational basis to optimize these uses, thereby also allowing the development of yeast as a popular eukaryotic model system. This model led to a cornucopia of seminal discoveries in cell biology. For about two decades yeast has also been used as a model and a tool for therapeutic research, from the production of therapeutics and the development of diagnostic tools to the identification of new therapeutic targets, drug candidates and chemical probes. These diverse chemobiological applications of yeast are presented and discussed in the present review article.

Cross-Species Complementation of Nonessential Yeast Genes Establishes Platforms for Testing Inhibitors of Human Proteins

Cross-species complementation can be used to generate humanized yeast, which is a valuable resource with which to model and study human biology. Humanized yeast can be used as an in vivo platform to screen for chemical inhibition of human protein drug targets. To this end, we report the systematic complementation of nonessential yeast genes implicated in chromosome instability (CIN) with their human homologs. We identified 20 human-yeast complementation pairs that are replaceable in 44 assays that test rescue of chemical sensitivity and/or CIN defects. We selected a human-yeast pair (hFEN1/yRAD27), which is frequently overexpressed in cancer and is an anticancer therapeutic target, to perform in vivo inhibitor assays using a humanized yeast cell-based platform. In agreement with published in vitro assays, we demonstrate that HU-based PTPD is a species-specific hFEN1 inhibitor. In contrast, another reported hFEN1 inhibitor, the arylstibonic acid derivative NSC-13755, was determined to have off-target effects resulting in a synthetic lethal phenotype with yRAD27-deficient strains. Our study expands the list of human-yeast complementation pairs to nonessential genes by defining novel cell-based assays that can be utilized as a broad resource to study human drug targets.

Yeast as a tool to identify anti-aging compounds

In the search for interventions against aging and age-related diseases, biological screening platforms are indispensable tools to identify anti-aging compounds among large substance libraries. The budding yeast, Saccharomyces cerevisiae, has emerged as a powerful chemical and genetic screening platform, as it combines a rapid workflow with experimental amenability and the availability of a wide range of genetic mutant libraries. Given the amount of conserved genes and aging mechanisms between yeast and human, testing candidate anti-aging substances in yeast gene-deletion or overexpression collections, or de novo derived mutants, has proven highly successful in finding potential molecular targets. Yeast-based studies, for example, have led to the discovery of the polyphenol resveratrol and the natural polyamine spermidine as potential anti-aging agents. Here, we present strategies for pharmacological anti-aging screens in yeast, discuss common pitfalls and summarize studies that have used yeast for drug discovery and target identification.

Downregulation of microRNA-637 Increases Risk of Hypoxia-Induced Pulmonary Hypertension by Modulating Expression of Cyclin Dependent Kinase 6 (CDK6) in Pulmonary Smooth Muscle Cells

BACKGROUND The objective of this study was to investigate the molecular mechanism by which miR-637 interferes with the expression of CDK6, which contributes to the development of pulmonary hypertension (PH) with chronic obstructive pulmonary disease (COPD). MATERIAL AND METHODS We used an online miRNA database to identify CDK6 as a virtual target of miR-637, and validated the hypothesis using luciferase assay. Furthermore, we transfected SMCs with miR-637 mimics and inhibitor, and expression of CDK6 was determined using Western blot and real-time PCR. RESULTS In this study, we identified CDK6 as a target of miR-637 in smooth muscle cells (SMCs), and determined the expression of miR-637 in SMCs from PH patients with COPD and normal controls. We also identified the exact miR-637 binding site in the 3'UTR of CDK6 by using a luciferase reporter system. The mRNA and protein expression levels of CDK6 in SMCs from PH patients with COPD were clearly upregulated compared with the normal controls. Cells exposed to hypoxia also showed notably increased CKD6 mRNA and protein expression levels, and when treated with miR-637 or CDK6 siRNA, this increase in CKD6 expression was clearly attenuated. Additionally, cell viability and cell cycle analysis showed that hypoxia markedly increased viability of SMCs by causing an accumulation in S phase, which was relieved by the introduction of miR-637 or CDK6 siRNA. CONCLUSIONS Our study proved that the CDK6 gene is a target of miR-637, and demonstrated the regulatory association between miR-637 and CDK6, suggesting a possible therapeutic target for PH, especially in patients with COPD.