Use this URL to cite or link to this record in EThOS:
Title: Investigating the role of higher order chromatin structure and DNA damage complexity on ATM signalling and G2/M checkpoint arrest
Author: Brunton, Holly
ISNI:       0000 0004 2724 4902
Awarding Body: University of Sussex
Current Institution: University of Sussex
Date of Award: 2011
Availability of Full Text:
Access from EThOS:
Access from Institution:
In response to DNA double stranded breaks (DSBs), mammalian cells have evolved two major repair pathways, DNA Non Homologous End Joining (NHEJ) and Homologous Recombination (HR). The majority of DSB repair in G1 and G2 phase is repaired with fast kinetics by NHEJ in a pathway that involves the core NHEJ factors: Ku, DNA-PKcs, XLF, DNA Ligase IV and XRCC4. A subset of slow repairing DSBs also requires ATM and Artemis (Riballo et al, 2004). This slow component of repair represents DSBs that reside within highly compacted regions of the genome known as heterochromatin (HC) (Goodarzi et al, 2008). ATM functions at HC to mediate relaxation by phosphorylating the HC building factor KAP-1 (Goodarzi et al, 2008). Here I provide evidence that DSBs dependent upon Artemis for their repair also reside within regions of HC. However, unlike ATM, Artemis functions downstream of the HC relaxation process. In response to DSBs, ATM phosphorylates the histone variant H2AX (γH2AX). γH2AX acts as a docking site for the localized recruitment and activation of DNA Damage Response (DDR) proteins. The expansion of γH2AX can spread over megabases of DNA. Here I have shown that highly compacted KAP-1, MeCP2 and DNMT3B enriched chromatin acts as a barrier to IR induced γH2AX expansion. In patient cells deficient for MeCP2 or DNMT3B proteins, such as Rett syndrome (MeCP2 deficient) and Immunodeficiency centromeric-instability facial-anomalies syndrome (DNMT3B deficient), ATM and Chk2 signalling is heightened, which is reflected in a hypersensitive and prolonged G2/M checkpoint arrest. These findings suggest that higher order chromatin complexity is a barrier to ATM signalling to the checkpoint machinery. In the final section of my thesis, I addressed what affect DNA damage complexity exerts on checkpoint arrest. Using exposure to heavy ion irradiation, which induces complex DSBs, I observed larger γH2AX foci and prolonged G2/M checkpoint arrest.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QD0415 Biochemistry ; QH0426 Genetics ; QH0573 Cytology