CtIP contributes to non-homologous end joining formation through interacting with ligase IV and promotion of TMZ resistance in glioma cells

B. Yang, N. Han, J. Sun, H. Jiang, H.-Y. Xu

Ophthalmologic Department, China-Japan Union Hospital of Jilin University, Changchun, China. xuhaiyang76@163.com

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• Oncology

OBJECTIVE: C-terminal-binding protein interacting protein (CtIP) participates in a variety of DNA metabolisms and DNA double strand break repair (DSBR). The role of CtIP has been proven in facilitating end resection in homologous recombination (HR). This study aimed to investigate the role of CtIP in non-homologous end joining (NHEJ) formation.

MATERIALS AND METHODS: In this study CtIP deficient U87 cell line was generated by using CRISPR/Cas9 method. HR and NHEJ reporter assay were conducted in U87 cells. The cell viability of U87 cells was evaluated by using Sulforhodamine B (SRB) assay. Ionizing radiation assay and clonogenic survival assay were also conducted in this study. Bacteria expressed CtIP and ligase IV proteins were collected and purified. Affinity capture assay was conducted to observe the interactions between proteins.

RESULTS: Both of the temozolomide (TMZ)-resistant and CtIP deficient glioma cell lines were successfully generated. The results indicated that CtIP participated in NHEJ formation through interacting with ligase IV in glioma cells. CtIP significantly improved the NHEJ efficiency in glioma cells. The CtIP deficient glioma cells were sensitive to the treatment of DNA damaging drug (TMZ). Meanwhile, the CtIP deficiency significantly enhanced the sensitivity of glioma cells to the treatment of TMZ.

CONCLUSIONS: The present study indicated that CtIP contributed to NHEJ formation through interacting with IV and promotion of TMZ resistance in glioma cells via promoting DSBR efficiency.

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