Replication fork stalling is a source of potentially tumourigenic genomic instability. The RecQ family helicase, Rqh1, is critical for the prevention of replication fork collapse and the formation of potentially deleterious recombination intermediates following fork stalling. Previous work in our lab with Schizosaccharomyces pombe (fission yeast) has shown that rqh10/rqh10 diploids are inherently unstable and show rapid reversion to the haploid state. The current work exploits this characteristic of fission yeast rqh10 mutants in a screen for genes that normally promote replication associated genomic instability. The rqh10rad30 mutant strains employed in this work incorporate the checkpoint deficiency caused by a lack of Rad3, so as to exacerbate the genomically unstable nature of this model. The current work describes the lithium acetate transformation based random mutagenesis by non-homologous integration of the ura4+ selectable marker into the rqh10rad30 fission yeast strains. This random mutagenesis generated extensive (24,500 – 50,000) mutant libraries. The quality of the libraries was assessed by can1 mutant assay, confirming an adequately extensive mutagenesis for the proposed screen. The process to be employed in the screen would involve the crossing of the mutant libraries, with the hope of generating diploids that will have two mutant copies of the same gene. Some of these diploids would appear unusually stable, showing a normal sporulation phenotype. This would indicate the mutation of a gene that normally promotes genomic instability following replication fork stalling. The practicality of the proposed screen of a vast number of diploids was assessed and described in detail in the current work. A technique involving inverse PCR (IPCR) adopted from previous work to identify mutants of interest, was also investigated. The investigation of this technique, and the work of others, suggests that transformation using such selectable marker fragments results in most apparent transformants containing extrachromosomal ura4+ fragments. These fragments are thought to provide the predominant template for IPCR, rendering the process unsuccessful at identifying the mutation in the current screen. However, with the mutant libraries generated, and the screen procedure detailed, the stage is set to conduct the screen once a more appropriate mutation location technique is identified. / Thesis (Master, Pathology & Molecular Medicine) -- Queen's University, 2008-05-31 22:25:14.009

Transient replication assays have identified a late expression factor 3, LEF-3, to be essential for DNA replication and late gene expression in the baculovirus species, AcMNPV. Although its specific role in these two processes has not been determined, this single-stranded DNA binding protein is multi-functional. LEF-3 forms a homo-oligomer, binds single-stranded DNA, interacts with components of the viral replication complex and is required to transport the helicase protein P143 into the nucleus of infected cells. Various regions within LEF-3 were deleted to determine the domain essential to its function and the N-terminal amino acids 1-125 were found to be sufficient for late gene expression. This N-terminal region includes the 56 amino acid region of LEF-3 required for nuclear transport. In order to define this domain, the effect of site-specific mutagenesis of LEF-3 on its intracellular distribution was determined. Fluorescence microscopy of expression plasmid transfected cells demonstrated that amino acids 14 to 37 formed the core nuclear localization signal (NLS), but the flanking amino acids may act as regulatory elements. Comparison with other group 1 Alphabaculoviruses suggested that this core region contained a functionally duplicated NLS. The AcMNPV LEF-3 also functioned in mammalian cells indicating that the protein nuclear import systems in insect and mammalian cells are conserved. Mutagenesis of two conserved cysteine residues located at amino acids 82 and 106 were not essential for nuclear localization or for interaction with P143. However, by using a modified construct of P143 that localized on its own to the nucleus, it was demonstrated that a functional nuclear localization domain on LEF-3 was required for an interaction between LEF-3 and P143. / Thesis (Master, Microbiology & Immunology) -- Queen's University, 2009-01-04 18:25:23.7

The objective of this thesis is to synthesize and examine the photophysical and structural properties of 3-(pyridin-2-yl)imidazo[1,5-a]pyridine (P) and 3-(pyridin-2-yl)imidazo [1,5-a]pyridine (IQ) based cations and their potential use as DNA binding agents. The P ligand was aimed to compare with the IQ ligand as they have similar structures. Two series of compounds were synthesized; one series comprising organic cations, including PC2, PC3, PC4, IQC2 and IQC3. The other one contains ruthenium complexes Ru(bpy)2P, Ru(bpy)2IQ and Ru(P)3). Compounds were prepared as Cl-, Br- and/or PF6- salts. All compounds were characterized by NMR, UV-vis, luminescescence and electrochemistry, when applicable. The results show that P and IQ based organic cations have similar electrochemical properties, and may be candidates for guanine photo-oxidation. However, [Ru(bpy)2P](PF6)2, [Ru(bpy)2IQ](PF6)2 and [Ru(P)3](PF6)2 do not seem to have reduction potentials in the excited states that are appropriate for nucleic base photo-oxidation. / Thesis (Master, Chemistry) -- Queen's University, 2009-09-01 11:58:42.728

The human Rad9A checkpoint protein is required for genomic stability and proper execution of the DNA damage checkpoint. Previous work has shown Rad9A to be the key member of a heterotrimeric toroidal structure known as the 911 complex, along with Hus1A and Rad1, which is similar in structure to PCNA. Recent literature suggests Rad9A is a novel oncogene, found to be upregulated in a number of cancers and high mRNA levels are thought to have a protective effect on tumour growth. This thesis describes two novel functions for the Rad9A protein. The first is as a facilitator for the nuclear translocation of the Claspin adaptor protein, required for successful Chk1-mediated checkpoint activation. The second is as part of a novel nuclear structure containing important members of the homologous recombination DNA repair pathway. Work described herein also confirms the existence of a Rad9A paralogue, Rad9B, that partially rescues defects associated with Rad9A-deficiency and is expressed in both tumour and undifferentiated embryonic stem cell lines. This work discusses these findings in the context of current literature and provides future experiments to continue investigations into the function of this vital checkpoint protein. / Thesis (Ph.D, Biochemistry) -- Queen's University, 2010-03-26 12:02:41.304

No description available.

No description available.

The synthesis of the tertbutyldimethylsilyl derivatives of adenosine is described. The 2',5'-protected nucleosides were rapidly and easily prepared in relatively good yields. / The silylated nucleosides are easily incorporated into ribonucleotides using the fast and efficient dichlorophosphite method. The ribonucleotide GpCpApApCpCpA corresponding to the 3'-terminus of / (DIAGRAM, TABLE OR GRAPHIC OMITTED...PLEASE SEE DAI) / was successfully synthesized in a stepwise fashion. The stepwise and block condensation pathways were compared in the synthesis of CpCpCpCpC. The syntheses of A2'p5'A2'p5'A and other 2',5'- and symmetrically-linked ribonucleotides were readily accomplished. ('31)P NMR was very useful in elucidating the structure of the diribonucleoside monophosphates. A study of the effect of temperature and solvents on yield of final product is undertaken. Various phosphate protecting groups are also evaluated. / A suitable deprotection procedure is investigated and the identity of the phosphate linkages confirmed by enzyme degradations.

No description available.

No description available.

No description available.