The role of p97/VCP co-factor UBXD8/FAF2 in DNA damage response

Thesis

The homohexameric AAA ATPase p97, also known as valosin-containing protein (VCP), is a fundamentally important molecular chaperone in DNA damage repair. It interacts with its co-factors and uses ATPase activity to control ubiquitin- and SUMO-mediated protein turnover and degradation. SILAC-based quantitative mass spectrometry identified that the p97 co-factor UBXD8/FAF2 significantly increases its interaction with p97 on chromatin during cell recovery after ionising radiation. UBXD8, also known as Fas-associated factor 2 (FAF2), was also shown to have a putative SUMO-interacting motif (SIM). The literature so far has described UBXD8 as an endoplasmic reticulum (ER)-associated degradation protein and a p97 recruitment factor for de novo fatty acid synthesis in lipid droplets. Its role on chromatin after DNA damage, however, is unknown. This thesis characterises a role of UBXD8 in DNA damage response and observes how its function relates to p97 on DNA damage sites.

This study discovered that UBXD8 and p97 regulate levels of SUMO-1 and SUMO-2/3 on DNA damage. Depletion of either leads to the accumulation of sumoylated substrates over 6 hours after DNA damage induction. The kinetics of SUMO regulation is similar in the absence of UBXD8 and p97, raising the possibility that UBXD8 works in a complex with p97 to remove sumoylated proteins from chromatin. The study further demonstrated that UBXD8 itself is recruited to and regulates the recruitment of p97 to DNA damage, consequently having an effect on ubiquitylation.

These results introduce a potential novel component in DNA damage response. The potential clinical benefit of studying p97 and its co-factors is the specific targeting of p97 function in DNA repair that could provide a way to sensitise cancer cells to radiotherapy.

Authors: Kilgas, S

• DOI: 10.5287/ora-qrjebzz0g
• Type of award: MSc by Research
• Level of award: Masters
• Awarding institution: University of Oxford
• Language: English