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No description available.

RNA is recognised as an important biomolecule involved in many broad cellular functions such as transcription, translation regulation and protein synthesis. Most pathogenic viruses replicate their genome as RNA during some stages in their life cycle. There is an urgent need to develop new methods to treat numerous viral diseases by targeting RNA and to understand the processes by which RNA-protein complexation can be inhibited. Our study focuses on the interactions between the HIV-1 Rev Responsive Element RNA (RRE) with a series of aminoglycosides developed jointly between our group in Manchester and GSK (USA). Even though a number of novel aminoglycoside have been explored previously, they are complex, large molecular weight compounds with low specificity, which limits their use as RNA recognition ligands and anti-viral drugs. The key problem is to be able to synthesise precursors by short, direct routes, avoiding significant detours caused by traditional carbohydrate protecting group strategies, while still delivering sterocontrol and opportunities to diversify. In chapter II we describe our efforts to synthesize the 6-glucosamine moiety (A-ring). A flexible synthesis of 6-aminoglucosamine derivatives can be accomplished in 5 steps using a totally regioselective enzymatic hydrolysis, controlled oxidation to sensitive but manageable aldehydes (hitherto rarely accomplished with a C-4 OAc), and reductive amination technology that allow for unprecedented diversification. In a different approach stereocontrolled synthesis of a model compound was achieved in 4 steps including a novel TEMPO oxidation and a one-pot oxidation/imine-reduction for the complete synthesis of the molecule.Chapter III describes our attempts towards the development of a robust stereoselective O-glycosylation strategy using Lewis acids. In pursuance of an efficient synthesis of our designed RNA binder target compound the stereoselective formation of the glycosidic linkage connecting the A-ring with the 2-DOS ring is an important step. This chapter also gives a general overview of the challenges involved in glycosylation followed by the strategies we employed to overcome some of these issues. We discuss our unusual stereocontrolled glycosylation in which, despite a neighbouring “participatory” group at C-2, the α-glycoside is delivered in high yield. This result implies that the reaction does not occur through a conventional neighbouring group participation.

Η ριβονουκλεάση Ρ (RNase P) είναι μια πανταχού παρούσα ενδονουκλεάση, και σε πολλές περιπτώσεις αποτελεί ένα ριβοένζυμο, η οποία συμμετέχει στον μηχανισμό ωρίμανσης των πρόδρομων tRNAs. Στην πλειοψηφία των περιπτώσεων είναι ένα ριβονουκλεοπρωτεϊνικό σύμπλοκο που αποτελείται από μια RNA υπομονάδα και τουλάχιστον μια πρωτεϊνική υπομονάδα. Όσον αφορά τα ευκαρυωτικά κύτταρα, πιστεύεται πως υπάρχουν δυο διακριτές μορφές του ολοενζύμου, μια πυρηνική και μια μιτοχονδριακή. Στο Saccharomyces cerevisiae η μιτοχονδριακή RNase P διαθέτει μια RNA και μια πρωτεϊνική υπομονάδα που κωδικοποιούνται από ένα μιτοχονδριακό (rnpB) και ένα πυρηνικό γονίδιο, αντίστοιχα. Σε αυτήν την εργασία απομονώσαμε και μερικώς καθαρίσαμε την μιτοχονδριακή RNase P από τον Schizosaccharomyces pombe. Κλωνοποιήθηκε, επίσης, το γονίδιο που κωδικοποιεί την RNA υπομονάδα της μιτοχονδριακής RNase P. Αυτό το ένζυμο παρουσιάζει διαφορετική εξειδίκευση για τα υποστρώματα SupS1 (pre-tRNASer) και pre-tRNATyr και δεν απενεργοποιείται από την μικροκοκκική νουκλεάση. / Ribonuclease P is a universally conserved ribozyme that it is involved in the 5΄ maturation of precursors tRNAs. It is in most cases a ribonucleoprotein complex which comprises an RNA subunit and at least one protein subunit. Concerning the eukaruotic cells, it is expected that distinctive nuclear and mitochondrial RNase P activities exist. In Saccharomyces cerevisiae the mitochondrial RNase P consists of an RNA and a protein subunit encoded by a mitochondrial (rnpB) and a nuclear gene, respectively. In the present study we isolated and partially purified mitochondrial RNase P from Schizosaccharomyces pombe and we cloned the gene that encodes the mitochondrial RNase P RNA subunit. This enzyme exhibits different specificity on SupS1 and pre-tRNATyr substrates and is not inactivated by micrococcal nuclease.