Unveiling novel participants in the DNA damage response

Thesis

The human genome is constantly challenged by DNA damage resulting from environmental factors and metabolic processes. To safeguard the integrity of the genome, a complex defence system known as the DNA damage response (DDR) has evolved. The DDR comprises intricate mechanisms, including DNA repair pathways, damage tolerance processes, cell cycle checkpoints and programmed cell death, together aimed at maintaining genomic stability. Among the various types of DNA lesions, interstrand crosslinks (ICLs) pose a significant threat as they impede DNA replication and transcription. Inadequate repair of ICLs is closely linked to Fanconi anaemia (FA), a genetic disorder associated with severe health consequences. Moreover, ICL-inducing agents have a broad clinical application in cancer therapy, although the emergence of drug resistance poses a challenge. Therefore, comprehending the mechanisms involved in ICL repair is critical for developing alternative treatment strategies and enhancing drug sensitivity.

The focus of this DPhil thesis is to investigate the participation and function of two novel proteins in the cellular response to ICL-induced DNA damage. Rapid accumulation of the first protein at ICL sites is observed, and its knockout results in heightened cellular sensitivity to ICL-inducing agents, indicating its positive contribution to cell survival against ICLs. Further investigations revealed that this protein operates independently of the established FA and NEIL3 pathway for ICL repair, suggesting its potential role in alternative repair mechanisms or early-stage DDR processes. The second novel protein exhibits a distinct relocation from the nucleoplasm to the peripheral nucleoli, forming a ring-shaped accumulation pattern in response to ICLs. Additional experiments demonstrate that this protein translocates into the nucleolar cap under nucleolar stress induced by various types of DNA damage and transcription inhibition. These findings support the notion that the nucleolus acts as a stress sensor, and the nucleolar translocation of this novel protein potentially contributes to cellular fate decisions or the interplay between DDR and nucleolar function. Together, the research presented in this thesis provides insights into the roles of two new protein players in preserving genomic stability. Understanding their interactions with established repair pathways and their potential therapeutic implications in FA and cancer treatment will pave the way for developing targeted interventions and improving patient outcomes.

Authors: Li, S

• DOI: 10.5287/ora-9e26qdwz9
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Keywords: Interstrand crosslink (ICL); DNA damage response (DDR); Fanconi anaemia (FA); Nucleolar Stress
• Subjects: DNA damage