Maintenance of genome stability through histone ADP-ribosylation

Maintaining genome integrity through DNA repair is critical for human health and defects in these pathways result in cancer, neurodegeneration and premature ageing. Understanding DNA repair mechanisms will provide insights into the underlying causes of these conditions and strategies for their treatment. For example, inhibitors of Poly(ADP-ribose) polymerases (PARPs), enzymes that regulate DNA strand break repair, are used to treat DNA repair deficient tumours, with the potential to treat other malignancies.

However, despite the use of PARP inhibitors in the clinic, the substrates modified by these enzymes and how they regulate DNA repair are ill-defined. For example, although histones are targets for ADP-ribosylation (ADPr) following DNA damage, how this regulates genome stability either directly, or through competition with other histone post-translational modifications (PTMs) is unclear.  This, in part, is due to the absence of an experimental platform in which PARPs and histone ADPr sites can be manipulated in tandem. These criteria are met in the eukaryotic model organism Dictyostelium and we have identified histone ADPr sites modified in response to DNA damage in this organism. We will exploit the unique ability to introduce site-specific ADPr mutations into endogenous Dictyostelium histone genes to define how ADPr regulates DNA repair either directly, or through influencing other histone PTMs. We will identify novel proteins that specifically interact with ADPr histones and characterise these factors in human cells. Together, this work will uncover how cells maintain genome integrity that will inform novel strategies to refine the use of PARP inhibitors in the clinic.