USP17L2-SIRT7 axis regulates DNA damage repair and chemoresistance in breast cancer cells.

PURPOSE

Sirtuin7 (SIRT7), as a member of the sirtuin and NAD-dependent protein-modifying enzyme family, plays an important role in regulating cellular metabolism, stress responses, tumorigenesis, and aging. Ubiquitination and deubiquitination are reversible post-translational modifications that regulate protein stability, enzyme activity, protein-protein interactions, and cellular signaling transduction. However, whether SIRT7 is regulated by deubiquitination signaling is unclear. This study aims to elucidate the molecular mechanism of SIRT7 via deubiquitination signaling.

METHODS

USP17L2 or SIRT7-targeting shRNAs were used to deplete USP17L2 or SIRT7. Western blot was applied to assess the effects of USP17L2 or SIRT7 depletion. A co-immunoprecipitation assay was used to detect the interaction relationship. Cell Counting Kit-8 assays were applied to assess the viability of breast cancer cells. An immunohistochemistry assay was employed to detect the protein level in samples from breast cancer patients, and the TCGA database was applied to analyze the survival rate of breast cancer patients. Statistical analyses were performed with the Student's t test (two-tailed unpaired) and χ test.

RESULTS

We find that the deubiquitinase USP17L2 interacts with and deubiquitinates SIRT7, thereby increasing SIRT7 protein stability. In addition, USP17L2 regulates DNA damage repair through SIRT7. Furthermore, SIRT7 polyubiquitination is increased by knocking down of USP17L2, which leads to cancer cells sensitizing to chemotherapy. In breast cancer patient samples, high expression of USP17L2 is correlated with increased levels of SIRT7 protein. In conclusion, our study demonstrates that the USP17L2-SIRT7 axis is the new regulator in DNA damage response and chemo-response, suggesting that USP17L2 may be a prognostic factor and a potential therapeutic target in breast cancer.

CONCLUSION

Our results highlighted that USP17L2 regulates the chemoresistance of breast cancer cells in a SIRT7-dependent manner. Moreover, the role of USP17L2 as a potential therapeutic target in breast cancer and a prognostic factor for patients was elucidated.