ESTRO 2024 - Abstract Book

S5380

Radiobiology - Tumour biology

ESTRO 2024

Zhuang Liu 1 , Mingming Xiao 1 , Han Wang 2 , Bo Xu 3

1 Tianjin Medical University Cancer Hospital and Institute, Biochemistry and Molecular Biology, Tianjin, China. 2 Chongqing University School of Medicine, Intelligent Oncology, Chongqing, China. 3 Chongqing University Cancer Hospital, Intelligent Oncology, Chongqing, China

Purpose/Objective:

The DNA damage response (DDR), orchestrated by a series of post-translational modifications of critical proteins, is a crucial mechanism to guard against genetic instability and to promote cell survival in response to DNA damaging agents such as ionizing radiation. ZDHHC family -mediated S-palmitoylation is the major mechanism regulating protein localization, stability, interaction. Altered S-palmitoylation is associated with the initiation and progression of malignant tumors, however, its role in the DDR and the radiosensitivity remains unclear. This study aims to elucidate the molecular mechanism by which ZHHC20 regulates DNA damage repair and radiosensitivity.

Material/Methods:

In this study, we screened all 23 palmitoyl acyltransferase ZDHHC family members for their roles in the DNA damage response by siRNA and shRNA libraries. We also generated ZDHHC20 knockout mice and characterized the mouse response to ionizing irradiation induced DNA damage in vivo . Further, by whole proteomic palmitoylation mass spectrometry, we mapped interacting proteins and their associated cestine sites for palmitoylation. By the acyl biotinyl exchange method, we revealed that KAP1/Trim28 was palmitoylated by ZDHHC20. Using a CRISPR-cas9 system in which Kap1 palmitoylation is mutated, we investigated the functional significance of Kap1 palmitoylation in the DDR and radiosensitivity.

Results:

We identified ZDHHC20 as the most prominent involved in DNA damage repair and radiosensitivity.

There were 311 proteins that were palmitoylated in a ZDHHC20-dependent manner. Among them, 7 interacted with ZDHHC20.

We found that ZDHHC20-dependent KAP1 palmitoylation enhanced the phosphorylated form of KAP1 interacting with chromatin, hence promoting 53BP1 and BRCA1 recruitment.

Exploring upstream regulatory signals, we found that DNA damage promoted Ataxia-Telangiectasia Mutated (ATM) - dependent phosphorylation of ZDHHC20 at Serine 339, which enhances KAP1 palmitoylation.

Conclusion:

Together, our findings elucidate the regulatory mechanism of ZDHHC20 palmitoyl acyltransferase in the DNA damage response and radiosensitivity. This will be of great significance for further elucidating the role of palmitoyl modification in the repair of cellular DNA damage induced by IR and for providing a new strategy for molecular radiosensitization.