Award details

Characterisation of the role of oxidised protein hydrolase in the molecular and cellular response to chromosome damage

Reference	BB/C516595/1
Principal Investigator / Supervisor	Professor Keith Caldecott
Co-Investigators / Co-Supervisors
Institution	University of Sussex
Department	Genome and Damage Stability Centre
Funding type	Research
Value (£)	185,266
Status	Completed
Type	Research Grant
Start date	14/11/2005
End date	13/11/2008
Duration	36 months

Abstract

The genetic material in human cells is continuously damaged by reactive oxygen species that arise endogenously in our cells as intermediates of cellular metabolism, and from genotoxins present in our environment. Consequently, cells possess efficient mechanisms for repairing chromosomal DNA. Recently, we employed a genetic screen to identify novel protein partners of human XRCC1, a protein that is essential for embryonic viability in mouse and which plays a critical role in recruiting and stimulating proteins required for the repair of chromosomal single-strand breaks. This work has identified a novel and unexpected interaction between XRCC1 and oxidised protein hydrolase (OPH), a polypeptide that possesses the ability to degrade, specifically, oxidatively damaged proteins. Moreover, by employing GFP-tagged OPH in immunofluorescence experiments, we have observed that OPH is recruited to sites of chromosomal oxidative damage in an XRCC1-dependent manner. Within chromosomes, DNA is wrapped around a central core of histone proteins in a compact structure known as chromatin. During oxidative attack of DNA, histones and other chromatin proteins (e.g. HMG proteins) can also be damaged either by the reactive oxygen species or during the process of DNA repair itself. The latter observation emerges from the observation that ADP-ribose, which is produced in high localised concentrations by poly (ADP-ribose) polymerase and poly (ADP-ribose) glycohydrolase during the signalling of chromosome DNA strand breaks, is a potent inducer of histone carbonylation. If allowed to persist, damaged histones and other chromatin proteins can hinder processes involved in chromosome maintenance and metabolism, including transcription and DNA repair. In vivo, the risk of accumulating oxidised histones or other chromatin proteins is most likely particularly pronounced in post-mitotic cells, because in cycling cells half of the chromosomal histone complement is replaced each cell cycle. In agreement with this, elevated levels of oxidised histones, as measured by levels of protein carbonylation, have been observed in ageing cells and in a variety of ageing disorders. Despite the importance of chromatin architecture on normal cellular physiology, however, little or nothing is known about whether or how damaged histones and/or other chromatin proteins are replaced. We thus propose that the interaction between XRCC1 and OPH represents a novel mechanism by which damaged histones and/or other chromatin proteins can be repaired. We suggest that, in addition to recruiting DNA repair proteins to sites of broken chromosomes, XRCC1 also recruits oxidised protein hydrolase in order to facilitate the removal and subsequent replacement of damaged histones with undamaged ones. In the proposed project, we will employ a combination of standard biochemical, microscopic, and cellular techniques (as described in detail in the Case For Support) to test this hypothesis and to identify the role and importance of OPH and its interaction with XRCC1 in the response of mammalian cells to chromosome damage.

Summary

unavailable

Committee	Closed Committee - Biochemistry & Cell Biology (BCB)
Research Topics	X – not assigned to a current Research Topic
Research Priority	X – Research Priority information not available
Research Initiative	X - not in an Initiative
Funding Scheme	X – not Funded via a specific Funding Scheme

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