TBX20 inhibits colorectal cancer tumorigenesis by impairing NHEJ-mediated DNA repair.

DNA high methylation is one of driving force for colorectal carcinoma (CRC) pathogenesis. Transcription factors (TFs) can determine cell fate and play fundamental roles in multistep process of tumorigenesis. Dysregulation of DNA methylation of TFs should be vital for the progression of CRC. Here, we demonstrated that TBX20, a T-box TF family protein, was downregulated with hypermethylation of promoter in early-stage CRC tissues and correlated with a poor prognosis for CRC patients. Moreover, we identified PDZRN3 as the E3 ubiquitin ligase of TBX20 protein, which mediated the ubiquitination and degradation of TBX20. Furthermore, we revealed that TBX20 suppressed cell proliferation and tumor growth through impairing non-homologous DNA end joining (NHEJ)-mediated double-stranded break repair by binding the middle domain of both Ku70 and Ku80 and therefore inhibiting their recruitment on chromatin in CRC cells. Altogether, our results reveal the tumor-suppressive role of TBX20 by inhibiting NHEJ-mediated DNA repair in CRC cells, and provide a potential biomarker for predicting the prognosis of patients with early-stage CRC and a therapeutic target for combination therapy.