The role of PARPs and APLF in DNA interstrand crosslink repair

Thesis

Over the duration of every organism’s life its cells continuously face insults to their DNA. The accumulation of lesions results in cell death, inflammation and, following the activation of oncogenes or inactivating mutations of DNA repair factors, cancer formation. One particularly deleterious form of DNA damage are DNA interstrand crosslinks (ICLs), which prevent DNA strand seperation, therefore interfering with replication and transcription. Here we uncover a novel function for PARPs and the DNA repair protein APLF in the tolerance of human cells to DNA ICLs. Consistent with a role of PARPs in ICL repair, we observe ADP-ribosylation in response to the ICL inducing agent cis-platin. Furthermore, the inhibition of PARPs by Olaparib sensitizes human cells to ICLs. We identify the importance of PARP1 and PARP2 in these events and uncover that they are epistatic. We propose that PARP1 and PARP2 participate in ICL removal and that this is independent of the Fanconi Anemia pathway. The NHEJ repair factor APLF is recruited to chromatin in response to DNA ICLs and localizes to sites of laser induced damage in combination with the photreactive ICL inducing drug 4,5',8-trimethylpsoralen. Disruption of APLF sensitizes cells to ICLs. Additionally, the ADP-ribose binding tandem PBZ domain of APLF is essential for the restoration of MMC tolerance in aplfΔ cells. We suggest that APLF is an early responder to ICL formation. Together these data identify a novel role for PARP1, PARP2 and APLF in the tolerance of human cells to ICLs.

Authors: Zobel, F

• DOI: 10.5287/ora-0z5rgbnnz
• Type of award: MSc by Research
• Level of award: Masters
• Awarding institution: University of Oxford