The role of ATM signalling and its mediator proteins in DNA double strand break repair

Kakarougkas, Andreas David William (2012) The role of ATM signalling and its mediator proteins in DNA double strand break repair. Doctoral thesis (PhD), University of Sussex.

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Abstract

Although most DNA double strand breaks (DSBs) are repaired by DNA nonhomologous
end!joining (NHEJ), DSBs at heterochromatin (HC) regions undergo repair
by homologous recombination (HR) in G2 phase. Repair of DSBs at HC regions
requires ATM-dependent KAP1 phosphorylation and subsequent HC relaxation. The
mediator proteins facilitate DSB repair at HC in G1 phase by retaining ATM and hence
pKAP1 at DSBs until the completion of repair. In this thesis, I investigated the role of
the mediator proteins in enabling DSB repair in G2 phase. I demonstrate that the
mediator proteins are required for the slow component of DSB repair in G2, which
represents HR. They also promote ATM-dependent pKAP1 formation in G2 as in G1.
In addition, I have described a role for MDC1 in Rad51 loading and for RNF8 in DNA
resection. Moreover, I demonstrate that BRCA1 overcomes an inhibitory barrier by
53BP1 to resection by promoting a G2!specific enlargement in 53BP1 foci during HR
that involves 53BP1 repositioning to the foci periphery and vacation from the central
core. RPA foci form in the core devoid of 53BP1. 53BP1 has opposing roles in HR; it
creates a restrictive barrier to resection but promotes pKAP1 and HC relaxation. RAP80
also inhibits resection by binding to ubiquitylated histones at DSBs. I demonstrate that
the DUB enzyme, POH1, is required to overcome the barrier posed to resection by
RAP80 since its depletion leads to deficient 53BP1 vacation of the central core and
deficient resection. BRCA1 and POH1 cooperate during G2 phase to promote resection
and DSB repair by HR. Additionally; I investigated the role(s) of the chromatin
remodelers BAF180 and CHD7 in transcriptional silencing following DSB induction, a
process that requires ATM, RNF8 and RNF168. I demonstrate that deficient
transcriptional silencing leads to a DSB repair defect at early times post IR.

Item Type: Thesis (Doctoral)
Schools and Departments: School of Life Sciences > Biochemistry
Subjects: Q Science > QD Chemistry > QD0241 Organic chemistry > QD0415 Biochemistry
Depositing User: Library Cataloguing
Date Deposited: 08 Oct 2012 14:18
Last Modified: 04 Sep 2015 15:34
URI: http://sro.sussex.ac.uk/id/eprint/40916

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