Paediatrics (RCH) - Theses

Permanent URI for this collection

http://hdl.handle.net/11343/200

Filters

2000 - 2010 2
1 1
2
Reset filters

Settings
Statistics
Citations
End date: 2010 × Subject: centromere ×

Search Results

Now showing 1 - 2 of 2
  • Item
    Thumbnail Image
    Human centromeric and neocentromeric chromatin
    Lo, Wing Ip Anthony ( 2000-09)
    Human centromeres contain large arrays of α-satellite DNA that are thought to provide centromere function. These arrays show size and sequence variations. However, the lower limit of the sizes of these DNA arrays in normal centromeres is unknown. Using a set of chromosome-specific α-satellite probes for each of the human chromosomes, interphase Fluorescence In Situ Hybridisation (FISH) was performed in a population screening study. This study demonstrated that extreme reduction of chromosome-specific α-satellite is unusually common in chromosome 21 (screened with the αRI probe), with a prevalence of 3.70%, compared to <=.12 % for each of chromosomes 13 and 17, and 0 % for the other chromosomes. No analphoid centromere was identified in over 17,000 morphologically normal chromosomes studied. All the low-alphoid centromeres are fully functional as indicated by their mitotic stability and binding to centromere proteins including CENtromere Protein-A (CENP-A), CENtromere Protein-B (CENP-B), CENtromere Protein-C (CENP-C), and CENtromere Protein-E (CENP-E). Sensitive metaphase FISH analysis of the low-alphoid chromosome 21 centromeres established the presence of residual αRI as well as other non-αRI α-satellite DNA suggesting that centromere function may be provided by (i) the residual αRI DNA, (ii) other non-αRI a-satellite sequences, (iii) a combination of i and ii, or (iv) an activated neocentromere DNA. (For complete abstract open document)
  • Item
    Thumbnail Image
    Functional analysis of a novel mammalian zinc-finger centromere protein, ZNF397
    Bailey, Sheena Louise ( 2010)
    The centromere is responsible for ensuring correct segregation of newly replicated sister chromatids into daughter cells. This fundamental role is conserved in eukaryotic organisms from yeast to humans. An error in chromosome segregation, including mutations in proteins that have a role in the assembly of the kinetochore, can result in daughter cells with an abnormal chromosomal number (aneuploidy). In humans, aneuploidy is a major contributor to birth defects, spontaneous abortions and infertility (Hassold and Hunt 2001), and is often associated with cancer due to the loss of tumour-suppressor genes or gain of oncogenes. A novel centromere protein, ZNF397, has recently been identified using a centromere positive autoimmune serum from a patient with watermelon stomach disease. ZNF397 protein belongs to the classical C2H2 group of the zinc-finger protein superfamily, which is one of the largest families in the human proteome. It contains two conserved domains; a leucine-rich SCAN domain and nine C2H2 zinc fingers. Bioinformatic analysis showed that ZNF397 is conserved in placental mammals. To date, only a few proteins containing zinc-finger domains have been identified at the centromeric or pericentric loci in various eukaryotic organisms. Stable human cell lines expressing a green fluorescent protein-ZNF397 fusion demonstrated that ZNF397 was centromeric and it co-localised with constitutive centromere protein CENP-A during interphase to early prophase of human cells. Deletion and domain-swap constructs indicated that the SCAN domain was necessary, but not sufficient, for centromere localisation. ZNF397 also localised to an active neocentromere, not the inactive α-satellite centromere on a pseudo-dicentric neocentromere chromosome four. Knockout studies in mice have revealed that ZNF397 was not essential for chromosome segregation, development or reproduction of the mice. The presence of ZNF397 in interphase cells but not on mitotic chromosomes suggests that it is not a constitutive structural protein and that it is unlikely to be directly involved in microtubule capture, mitotic segregation, or cytokinesis. An attractive hypothesis is that ZNF397 plays a role in the regulation of transcription at the centromere. Two possible mechanisms of action for ZNF397 are proposed; 1) ZNF397 could be directly involved in transcription of centromeric repeats or 2) ZNF397 could repress genes by recruiting them to the centromeric heterochromatin environment.