ETD Collection

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    Genotoxicity of mycotoxins in an improved drosophila wing spot test and other short-term effects
    (1992) Pacella, Rosana Elizabeth
    Attempts have been made recently to improve the Drosophiia Somatic Mutation and Recombination wing spot test (SMART) by inciudjig insecticide resistance genes that confer high bioactivation (HB) to SMART tester strains. A drawback of the HB lines is the presence of whorling of wing hairs which interferes with scoring for mutant spots. The gene responsible for this whorling effect, which I have named paisley (ply), was shown to be recessive and located around position 90 on chromosome 2 and is thus linked to the RI gene responsible for the high constitutive expression of cytochrome P450- dependent activities typical of HB strains. (Abbreviation abstract)
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    Temporal expression of Dmp53 and SNAMA isoforms and their relation to genotoxic stress.
    (2015) Nweke, Ekene Emmanuel
    RBBP6 is an E3 Ubiquitin ligase protein with a U-box motif. It interacts with p53 and Rb and is linked to several cellular functions. SNAMA is the Drosophila RBBP6 homolog, but is less characterized than its vertebrate counterparts. Gene expression studies on Drosophila have a potential to advance the knowledge on molecular mechanism underlying genotoxic stress. Previous studies have shown that SNAMA plays a critical role as an apoptosis suppressor and possibly in responses to genotoxic stress. The molecular basis for this is, however, unknown. Initially, two isoforms were identified by bioinformatics and one (Snama A) experimentally as well. Here, we confirm experimentally the existence of the second isoform (Snama B). We also show that these are differentially expressed during development and when the organism undergoes genotoxic stress. Total RNA samples were used to demonstrate gene expression by using Reverse Transcriptase Polymerase Chain Reaction. Using samples collected at different stages of development and from adult flies treated with the DNA damaging agent, irinotecan, it is shown that these isoforms are differentially expressed throughout development and upon genotoxic stress. This knowledge may help to understand the functional role SNAMA plays in normal physiology and in response to genotoxic stress. Furthermore, the results show that SNAMA is involved in a potentially beneficial intervention whereby the glycolytic pathway is bypassed by the addition of methyl pyruvate.
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    Protein interactions with drosophila p53
    (2014-09-23) Cajee, Umar-Faruq
    Drosophila melanogaster, a key model organism, has cognates of over 70% of human disease genes. This has created opportunities in the development of treatments for life threatening illnesses like cancer. Mutations on the p53 tumour suppressor protein, which is an activator of apoptosis, are common in many cancers. In mammals, p53 interacts with the Retinoblastoma Binding Protein 6 (RBBP6) which enhances the activity of MDM2, the prototypical negative regulator of p53, that is absent in invertebrates. In the absence of MDM2 the Drosophila RBBP6 homolog, SNAMA, through its DWNN Catalytic Module (DCM), is suspected to play an important role in the regulation of p53, probably via the ubiquitin proteasome pathway. Through bioinformatics analyses, and experimental analysis of transcripts, this study has shown the existence of two isoforms of SNAMA named here SNAMA A and SNAMA B for the long and short isoforms, respectively. SNAMA B appears to be expressed after genotoxic stress (DNA damage) in adults as well as during embryonic development. Recombinant protein expression in bacterial and yeast systems as well as HIS-tag chromatography and Western blot analyses were used to investigate interactions with Dmp53. Due to poor expression of recombinant Dmp53 protein in both prokaryotic and eukaryotic systems and unreliable commercial antibodies, it was impossible to complete interaction studies. Overall, these studies show that the SNAMA isoforms may play important roles during development and in response to DNA damage.