Mammalian telomeric DNA consists of tandem repeats of the sequence TTAGGG associated with a specialized set of proteins, known collectively as Shelterin. These telosomal proteins protect the ends of chromosomes against end-to-end fusion and degradation. The objective of this project was to investigate whether expression of Shelterin and Shelterin-associated proteins are altered, and influence the protection and maintenance of telomeres, in breast cancer cells. Initial findings showed that most of the Shelterin and Shelterin-associated genes were significantly down-regulated (at the mRNA expression level) in a panel of ten breast cancer cell lines. Epigenetic alterations to DNA (methylation at CpG Islands) and histones can result in altered expression of genes. Further investigations showed that the promoter region of POT1 was partially methylated in the breast cancer cell line, 21NT. To support these observations, a DNA methylation inhibitor, 5-aza-CdR, and a histone deacetylation inhibitor, TSA, were used in an attempt to reactivate the expression of silenced genes. This work generated novel findings. Treatment with 5-aza-CdR and TSA resulted in the highest recovery of TIN2 and POT1 mRNA levels at both short-term (48 and 72 hours) and long-term (3 weeks) treatment of the breast cancer cell line, 21NT cells. In addition, POT1 promoter methylation was analysed before and after treatment of 21NT cells. Bisulphite sequencing data were consistent with the mRNA expression results, showing up-regulation of POT1, as all methylation sites were demethylated after the treatment of 21NT cells with 5-aza-CdR. These studies also showed for the first time that both the short-term (72 hours) and 3 weeks treatment of 21NT cells with 5-aza-CdR was able to increase telomere lengths (using four measurement methods, i.e. TRF, q-PCR, flow-FISH and iQFISH). Breast cancer cell lines expressed low levels of several telosomal mRNAs and that this down-regulation was found to be due in part to promoter methylation. Methylation was shown to be relieved through treatment of the cells with 5-aza-CdR and TSA; specifically, POT1 was shown to be up-regulated to a higher extent compared with other Shelterin genes. Given that previous studies involved over-expression of POT1 in telomerase-positive cells to demonstrate telomere length elongation, we addressed the possibility that over-expression of POT1 may affect telomere length in 21NT breast cancer cells. The results showed that the average telomere length of the POT1 over-expressing clones was increased by 2 to 3 kb compared with 21NT non-transfected and empty vector controls. The study also demonstrated that increased telomere length (by ectopic over-expression of POT1) is not due to a direct effect of telomerase enzyme activity. One explanation for this could be that POT1 may induce a negative regulator of telomerase activity to maintain telomere length. Taken together, the results generated in this project suggest that POT1 may control a localised activation of telomerase enzyme at the telomere end, and regulate stability of the Shelterin complex.

Understanding the mechanisms plants utilize for seed storage protein (SSP) synthesis, transport and deposition have the potential rewards of enabling high yields of modified or foreign proteins. Hayashi et al. (1999) indicated that the machinery devoted to the synthesis of protein storage vacuoles in cotyledon cells can be induced in vegetative tissue by the constitutive expression of a pumpkin 2S albumin phosphinothricin-acetyl-transferase gene fusion (pumpkin 2S-PAT) resulting in the biogenesis of precursor-accumulating (PAC) vesicles in Arabidopsis leaves. This discovery was the impetus behind the work described which sought to examine this phenomenon further by ectopically evoking SSP trafficking and vesicle biogenesis machinery in leaves. With the aim of elucidating the mechanisms necessary to evoke PAC vesicle biogenesis, a suite of constructs including the pumpkin 2S-PAT and analogous napin-PAT and napin-GFP variants were synthesized. Analysis of these transgenes in Arabidopsis revealed that the pumpkin 2S albumin has a capacity unique from napin peptides to result in fusion protein accumulation. Further, the truncated pumpkin 2S albumin peptide and the pumpkin 2S albumin C-terminus were found to direct deposition to vesicles; however, the C-terminus alone was not enough to direct deposition to vesicles unless combined with a significantly shortened napin peptide. An increased ER protein throughput was correlated to trafficking of the fusion protein by Golgi-independent mechanisms resulting in stable accumulation of the unprocessed protein whereas less ER throughput indicated passage through the Golgi-dependent pathway resulting in accumulation of a processed variant. At the level of gene expression, as examined by a microarray study, both inducible and constitutive ectopic expression of pumpkin 2S-PAT resulted in substantial perturbations of the endomembrane system affecting protein folding, flowering time and ER-associated biosynthetic functions which indicated that modulation of flowering time and photoperiodism are highly dependent on protein trafficking and vacuolar biogenesis mechanisms and that high ER protein throughput occurs at the expense of biosynthesis and cessation of ER functioning.

No description available.

<p>Across the tree of life, novel genes are thought to be a source of much of the unique behaviors and adaptions between the different taxa. This is especially true in the social insects where novel genes are proposed to contribute to novel social behaviors. In the honey bee (Apis mellifera L.), a group of novel genes called the major royal jelly proteins (MRJPs) are proposed to be important to the expression of novel social behaviors, particularly those related to nursing versus foraging tasks. Unfortunately, identifying the functional role of novel genes is often not possible due to a lack of functional genomic tools in non-model species such as the honey bee. Here I have developed a novel ectopic expression system in Drosophila melanogaster and used it to elucidate how the MRJPs contribute to behavioral and transcriptional changes in the insect brain. I found that the MRJPs regulated the expression of hundreds of genes in Drosophila, and these overlap with genes regulated differentially between nursing and foraging honey bees. Furthermore, I found that MRJP expression impairs or negatively regulated phototaxis. My results demonstrate the MRJPs play a role in behavioral plasticity and highlight that the MRJPs may have a much larger role in the nurse-forager transition than previously thought.</p>