Orestes Tsolas

Bio: Orestes Tsolas is an academic researcher from University of Ioannina. The author has contributed to research in topics: Prothymosin Alpha & Histone H1. The author has an hindex of 23, co-authored 46 publications receiving 1473 citations.

Prothymosin alpha modulates the interaction of histone H1 with chromatin.

Abstract: Prothymosin alpha (ProTalpha) is an abundant acidic nuclear protein that may be involved in cell proliferation. In our search for its cellular partners, we have recently found that ProTalpha binds to linker histone H1. We now provide further evidence for the physiological relevance of this interaction by immunoisolation of a histone H1-ProTalpha complex from NIH 3T3 cell extracts. A detailed analysis of the interaction between the two proteins suggests contacts between the acidic region of ProTalpha and histone H1. In the context of a physiological chromatin reconstitution reaction, the presence of ProTalpha does not affect incorporation of an amount of histone H1 sufficient to increase the nucleosome repeat length by 20 bp, but prevents association of all further H1. Consistent with this finding, a fraction of histone H1 is released when H1-containing chromatin is challenged with ProTalpha. These results imply at least two different interaction modes of H1 with chromatin, which can be distinguished by their sensitivity to ProTalpha. The properties of ProTalpha suggest a role in fine tuning the stoichiometry and/or mode of interaction of H1 with chromatin.

Purification and properties of human placental ATP diphosphohydrolase.

Abstract: ATP diphosphohydrolase activity (ATP-DPH) has been previously identified in the paniculate fraction of human term placenta [Papamarcaki, T. & Tsolas, O. (1990) Mol. Cell. Biochem. 97, 1–8]. In the present study we have purified to homogeneity and characterized this activity. A 260-fold purification has been obtained by solubilization of the particulate fraction and subsequent chromatography on DEAE Sepharose CL-6B and 5′-AMP Sepharose 4B. The preparation has been shown to be free of alkaline phosphatase even though the placental extract is rich in this activity. The purified enzyme is a glycoprotein and migrates as a single broad band of 82 kDa on SDS/PAGE. The same band is obtained after photoaffinity labeling of the enzyme with 8–azido-[α-32P]ATP. The enzyme has a broad substrate specificity, hydrolyzing triphosphonucleosides and diphosphonucleosides but not monophosphonucleosides or other phosphate esters. The activity is dependent on the addition of divalent cations Ca2+ or Mg21. The Km values for ATP and ADP were determined to be 10μM and 20 μM, respectively. Maximum activity was found at pH 7.0–7.5 with ATP as substrate, and pH 7.5–8.0 with ADP. The enzymic activity is inhibited by NaN3 NaF3 adenosine 5′-[β,γ-imido]triphosphate and adenosine 5′-[α,β-methylene]triphosphate. Protein sequence analysis showed ATP-DPH to be N-terminally blocked. Partial internal amino acid sequence information was obtained after chymotryptic cleavage and identified a unique sequence with no significant similarity to known proteins. ATP-DPH activity has been reported to be implicated in the prevention of platelet aggregation, hydrolysing ADP to AMP and thus preventing blood clotting.

Metabonomics: a platform for studying drug toxicity and gene function

Abstract: The later that a molecule or molecular class is lost from the drug development pipeline, the higher the financial cost. Minimizing attrition is therefore one of the most important aims of a pharmaceutical discovery programme. Novel technologies that increase the probability of making the right choice early save resources, and promote safety, efficacy and profitability. Metabonomics is a systems approach for studying in vivo metabolic profiles, which promises to provide information on drug toxicity, disease processes and gene function at several stages in the discovery-and-development process.

Identification of Genes Periodically Expressed in the Human Cell Cycle and Their Expression in Tumors

Abstract: The genome-wide program of gene expression during the cell division cycle in a human cancer cell line (HeLa) was characterized using cDNA microarrays. Transcripts of >850 genes showed periodic variation during the cell cycle. Hierarchical clustering of the expression patterns revealed coexpressed groups of previously well-characterized genes involved in essential cell cycle processes such as DNA replication, chromosome segregation, and cell adhesion along with genes of uncharacterized function. Most of the genes whose expression had previously been reported to correlate with the proliferative state of tumors were found herein also to be periodically expressed during the HeLa cell cycle. However, some of the genes periodically expressed in the HeLa cell cycle do not have a consistent correlation with tumor proliferation. Cell cycle-regulated transcripts of genes involved in fundamental processes such as DNA replication and chromosome segregation seem to be more highly expressed in proliferative tumors simply because they contain more cycling cells. The data in this report provide a comprehensive catalog of cell cycle regulated genes that can serve as a starting point for functional discovery. The full dataset is available at http://genome-www.stanford.edu/Human-CellCycle/HeLa/.

Triglycerides and Cardiovascular Disease A Scientific Statement From the American Heart Association

Abstract: A long-standing association exists between elevated triglyceride levels and cardiovascular disease* (CVD).1,2 However, the extent to which triglycerides directly promote CVD or represent a biomarker of risk has been debated for 3 decades.3 To this end, 2 National Institutes of Health consensus conferences evaluated the evidentiary role of triglycerides in cardiovascular risk assessment and provided therapeutic recommendations for hypertriglyceridemic states.4,5 Since 1993, additional insights have been made vis-a-vis the atherogenicity of triglyceride-rich lipoproteins (TRLs; ie, chylomicrons and very low-density lipoproteins), genetic and metabolic regulators of triglyceride metabolism, and classification and treatment of hypertriglyceridemia. It is especially disconcerting that in the United States, mean triglyceride levels have risen since 1976, in concert with the growing epidemic of obesity, insulin resistance (IR), and type 2 diabetes mellitus (T2DM).6,7 In contrast, mean low-density lipoprotein cholesterol (LDL-C) levels have receded.7 Therefore, the purpose of this scientific statement is to update clinicians on the increasingly crucial role of triglycerides in the evaluation and management of CVD risk and highlight approaches aimed at minimizing the adverse public health–related consequences associated with hypertriglyceridemic states. This statement will complement recent American Heart Association scientific statements on childhood and adolescent obesity8 and dietary sugar intake9 by emphasizing effective lifestyle strategies designed to lower triglyceride levels and improve overall cardiometabolic health. It is not intended to serve as a specific guideline but will be of value to the Adult Treatment Panel IV (ATP IV) of the National Cholesterol Education Program, from which evidence-based guidelines will ensue. Topics to be addressed include epidemiology and CVD risk, ethnic and racial differences, metabolic determinants, genetic and family determinants, risk factor correlates, and effects related to nutrition, physical activity, and lipid medications. In the United States, the National Health and …