DNA Damage Response

Kristijan Ramadan

The research focus of the group is to understand the role of the ubiquitin-proteasome system (UPS) and its central component p97/VCP in genome stability. We aim to understand how can we use this knowledge to improve current cancer therapy, especially after ionizing radiation. p97/VCP is a evolutionarily conserved segregase that with the help of specific cofactors binds and remodels (segregates) diverse and mostly ubiquitinated proteins (substrates) in a variety of cellular processes and compartments. In this way p97/VCP and its cofactors play an essential role in the maintenance of protein balance (homeostasis) in the cell. We are especially interested in chromatin-related p97/VCP functions and consequently in chromatin-related protein homeostasis (Figure 1; p97/VCP-dependent chromatin-associated protein homeostasis) after DNA damage. Chromatin is the substance of a cell nucleus consisting of DNA, RNA and proteins, and the basic source of genetic information.

Using biochemical and cell biological approaches we are investigating fundamental molecular aspects of protein homeostasis in DNA replication, DNA repair and DNA damage response. Mechanistic insights of basic cellular processes related to DNA metabolism and related protein homeostasis can improve our knowledge of ageing and ageing related diseases as well as current diagnosis, prognosis and treatment of cancer.

We have identified the essential role of p97/VCP in chromatin and in DNA damage response, after ionizing and ultraviolet radiation. We have discovered a new human syndrome characterised by premature-ageing and early-onset hepatocellular carcinoma (Figure 2; green arrow indicates tumour mass) that is caused by mutations in p97-cofactor SPRTN (Figure 3; genomic localisation and protein structure of SPRTN with patient mutations).

Our results strongly suggest that protein-induced chromatin stress (PICROS; pathological accumulation of proteins on chromatin) plays an essential role in cancer and ageing. The group is currently trying to understand how chromatin-associated protein homeostasis regulates PICROS and thus prevents accelerated ageing and cancer. We believe that understanding of PICROS might open new avenues in cancer diagnosis, prognosis and therapy, but also answer fundamental questions about ageing.