Methylation of histone lysine residues functions as a dynamic, reversible mechanism for regulating gene expression and aberrations in this process have been linked with the development of cancer. Members of the lysine demethylase (KDM) family remove methyl marks from histones. KDM5B removes methyl marks from histone H3 lysine 4 (H3K4) whereas KDM6A and KDM6B remove methyl marks from histone H3 lysine 27 (H3K27). In this thesis, GSK-J4, an inhibitor of KDM5B, KDM6A and KDM6B, is shown to impair viability in a range of cancers affecting bone including multiple myeloma, Ewing sarcoma and chordoma. GSK-J4 induces a biphasic transcriptional response, characterized by an early, massive rise in the expression of a number of cysteine-rich metallothionein genes followed by induction of ATF4 via phosphorylation of eIF2α by GCN2. Induction of ATF4 leads to apoptosis in myeloma cells and cell cycle arrest in Ewing sarcoma. Ectopic overexpression of metallothioneins is shown to be sufficient to induce the ATF4 response. GSK-J4 is shown to alters cellular metabolism by impairing glutaminolysis. ChIPseq demonstrates a global increased H3K27me3 in response to treatment with GSK-J4 with a decrease in H3K4me3 around transcription start sites of genes not involved in the ATF4 response. Combined knockdown of KDM6A and KDM6B recapitulates the cellular response to GSK-J4 whereas inhibition of KDM5B is not sufficient to reproduce the effect. A model is presented suggesting that the increased requirement for incorporation of cysteine into protein due to the expression of metallothioneins leads to the presence of uncharged cysteinyl-tRNA molecules that are sensed by GCN2 leading to activation of an ATF4-driven integrated stress response.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:730193 |
| Date | January 2016 |
| Creators | Hookway, Edward |
| Contributors | Oppermann, Udo ; Athanasou, Nick |
| Publisher | University of Oxford |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | https://ora.ox.ac.uk/objects/uuid:b591861f-985b-4722-8027-492e750f3ff7 |
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