Massey Documents by Type

Permanent URI for this communityhttps://mro.massey.ac.nz/handle/10179/294

Browse

Filters

2014 - 201922020 - 20211

Settings

Subject: search.filters.subject.DNA repair

Search Results

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    Primary metabolic processes as drivers of leaf ageing
    (Springer Nature Switzerland AG, 2021-10) Kanojia A; Shrestha DK; Dijkwel PP
    Ageing in plants is a highly coordinated and complex process that starts with the birth of the plant or plant organ and ends with its death. A vivid manifestation of the final stage of leaf ageing is exemplified by the autumn colours of deciduous trees. Over the past decades, technological advances have allowed plant ageing to be studied on a systems biology level, by means of multi-omics approaches. Here, we review some of these studies and argue that these provide strong support for basic metabolic processes as drivers for ageing. In particular, core cellular processes that control the metabolism of chlorophyll, amino acids, sugars, DNA and reactive oxygen species correlate with leaf ageing. However, while multi-omics studies excel at identifying correlative processes and pathways, molecular genetic approaches can provide proof that such processes and pathways control ageing, by means of knock-out and ectopic expression of predicted regulatory genes. Therefore, we also review historic and current molecular evidence to directly test the hypotheses unveiled by the systems biology approaches. We found that the molecular genetic approaches, by and large, confirm the multi-omics-derived hypotheses with notable exceptions, where there is scant evidence that chlorophyll and DNA metabolism are important drivers of leaf ageing. We present a model that summarises the core cellular processes that drive leaf ageing and propose that developmental processes are tightly linked to primary metabolism to inevitably lead to ageing and death.
  • Thumbnail Image
    Item
    Role of N-terminal domains of p400 ATPase in the ATM interaction and DNA damage response : a thesis presented in partial fulfillment of the requirements for a the degree of Master of Science (MSc) in Genetics at Massey University, Manawatū, New Zealand
    (Massey University, 2016) Weber, Lauren Elizabeth
    Efficient repair of damaged DNA and preservation of genomic integrity is integral in the maintenance of proper cellular function and prevention of unrestricted cell proliferation. One critical threat to the stability of the genome is the double strand break (DSB), arguably one of the most cytotoxic lesions to DNA. Interference with the DSB repair mechanism can lead to dysregulation of cellular systems and the prospective development of malignancies. Two critical proteins in DBS repair are the Ataxia Telangiectasia Mutated (ATM) kinase, a serine/threonine kinase from the Phosphatidylinositol 3-Kinase-related Kinase (PIKK) family, and p400, an ATPase chromatin remodeler. ATM is one of the first responders to DSBs and is responsible for the phosphorylation of a multitude of protein substrates including the histone variant H2AX. Beyond its phosphorylation ability, ATM has been proposed as a potential shuttle for other repair machinery, aiding in the early and efficient recruitment of proteins to the DNA damage foci. One such proposed protein is p400. The exact role of p400 in DSB repair is unknown but previous studies show that there is a decrease in repair efficiency in its absence. A prospective interaction is supported by previous studies in which p400 and p400 N-terminal derivatives co-immunoprecipitate with ATM in vivo in HEK293T cells. This study aimed to confirm the interaction of ATM and p400 N-terminal derivatives in vitro and explore the functional implications of the association in vivo in U2OS cells. It was not possible to isolate full-length p400 derivatives in vitro and thus no conclusive results were obtained. Functional assays revealed the ability of one p400 fragment, F1, to inhibit DNA repair and cell proliferation after DNA double-strand break induction with bleomycin. Ectopic expression of the other two p400 N-terminal fragments, F2 and F3, induced an inhibition of cell proliferation under standard growth conditions. Although no conclusive results were acquired, a trend emerged suggesting that N-terminal fragment F1 is able to interfere with ATM protein-protein interactions resulting in a decrease in the efficiency of the DNA damage response and repair. These results implicate F1 as a potential target for further research in both DNA repair and cancer therapy.
  • Thumbnail Image
    Item
    ATM and p400 : characterisation of a novel interaction between a DNA repair enzyme and a chromatin remodeler : a thesis presented to Massey University in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Biochemistry
    (Massey University, 2014) Smith, Rebecca Jane
    The ability to maintain genomic integrity prevents unrestricted cell proliferation and the progression of cancer. DNA repair pathways such as the DNA double-strand break (DSB) response are essential in maintaining this integrity. This system requires activation of the serine/threonine kinase ataxia telangiectasia mutated (ATM) through acetylation by TIP60, a histone acetyl transferase, and subsequent ATM autophosphorylation. During DNA repair, activated ATM phosphorylates the histone variant H2AX several kilobases either side of the break site. This phosphorylation acts a signal for additional repair proteins and chromatin remodeling complexes which repairs DNA. In a previous study, H2AX phosphorylation was induced through the over expression of TIP60 or the SWI3-ADA2-N-CoR-TFIIIB (SANT) domain of p400. It was hypothesised that over expressed TIP60 or SANT domain was able to sequester a putative negative regulator from the ATM-TIP60 complex and artificially induce activation. This study aimed to investigate if a single domain of TIP60 or if a single helix from the three helix SANT domain was responsible for the activation of the ATM-TIP60 complex. Here, the ability of the chromo domain and zinc domain of TIP60 individually and the combined zincHat domain of TIP60 to induce H2AX phosphorylation as well as three helix deletion mutants of the SANT domain of p400 was examined. While all constructs were able to be expressed in human cell lines, the induction of H2AX was variable and non-reproducible. ATM belongs to the phosphatidylinositol 3-kinase-related kinase family (PIKK). Members of the PIKK family show domain homology, where the domain of one protein is replaced with the homologous domain of another member and the function of the protein is not altered. As p400 has been previously shown to interact with TIP60 and also Transformation/transcription domain-associated protein (TRRAP), a member of the PIKK family, it was hypothesised that p400 could interact with ATM (which also interacts with TIP60). This study confirms this novel interaction between ATM and p400 through the use of co-immunoprecipitation and protein localisation using confocal microscopy. This study provides a platform to further investigate the involvement of an ATM-p400 complex during DNA repair.