The demand for synthetic oligonucleotides has grown exponentially over the past decades as genome sequencing, functional genomics, polymerase chain reaction (PCR)-based detection methods, and gene silencing via RNA interference (RNAi) consume enormous numbers of DNA and RNA oligonucleotides. Although various RNA synthesis chemistries now allow oligoribonucleotides to be produced routinely, the higher complexity and cost of RNA (over DNA) has somewhat limited its availability. / A major goal of this thesis work was aimed at finding ribonucleoside synthons that potentially benefit two critical aspects of RNA manufacturing: yield and ease of post-synthesis processing. Towards these goals, we developed methods for the synthesis of RNA using 2'-O-Lv and 2'-O-acetal Lv (ALE) ribonucleoside derivatives. Deprotection of the RNA chains consisted of a three-step deprotection scheme, which eliminated the need for any harsh basic hydrolytic steps, generally composed of: (1) treatment with anhydrous NEt3 (r.t., 1 h) to deblock the phosphate's cyanoethyl groups; (2) hydrazinolysis (r.t., 30 min 4 h) to simultaneously deprotect the nucleobases and 2'-OH positions, and (3) fluoride treatment (r.t., 30 min) to effect cleavage from the controlled pore glass solid support. Significantly, the rather mild conditions to remove 2'-O-Lv or 2'-O-ALE protecting groups did not lead to RNA strand scission. Furthermore, in the case of 2'-O-ALE protection, higher step-wise monomer coupling yields (~98.7%) was possible, since the ALE protection is less bulky than conventional silyl protection, i.e. TBDMS. Furthermore, both 2'-O-Lv or 2'O-ALE chemistries are completely compatible with the synthesis cycles used by all automated gene synthesizers. / With adjustments in protecting group strategies for the 5'-OH, exocyclic amino nucleobase groups and the development of a light-labile solid support, two other major goals were achieved: (1) the first in situ synthesis of RNA on microarrays, and (2) synthesis of chemically modified RNA strands with 2'-O-acetal ester and 2'-O-acetal ester pyrrolidines in order to increase lipophilicity and cellular permeability over native RNA. When RNA synthesis was carried out with 5'-O-NPPOC 2'-O-ALE monomers on a microarray ("chip"), deprotection typically involved (1) cleavage of the photolabile 5'-protecting group; (2) treatment with anhydrous NEt3 (r.t., 1 h) to deblock the phosphate's cyanoethyl groups; (3) hydrazinolysis (r.t., 30 min 4 h) to simultaneously deprotect bases and 2'-OH positions. The latter step could also be accomplished with ethylenediamine at room temperature. An RNase A assay was performed as "proof-of-principle" to demonstrate the value of a DNA-RNA microarray for studying enzyme kinetics and specificity on oligonucleotide based libraries. We showed that RNase A acts effectively on a DNA-RNA substrate with measurable kinetics analogous to those of the reference substrates. / The novel 2'-O-modified RNA were tested as short interfering RNA pro-drugs ("pro-siRNA") that would cross the cell membrane and be hydrolyzed (at the 2'-O-ester groups) by ubiquitous esterases to release the active (siRNA) molecules. Indeed, both siRNA and pro-siRNA prepared via 2'-O-ALE chemistry were shown to be active in an RNAi luciferase gene knockdown assay, confirming the integrity of the synthesized RNA strands and the promise of the pro-siRNA approach.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.92290 |
| Date | January 2010 |
| Creators | Lackey, Jeremy |
| Contributors | Masad J Damha (Internal/Supervisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Chemistry) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | Electronically-submitted theses. |
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