UBE2T-regulated H2AX monoubiquitination induces hepatocellular carcinoma radioresistance by facilitating CHK1 activation

Abstract

Background Radioresistance is the major obstacle in radiation therapy (RT) for hepatocellular carcinoma (HCC). Dysregulation of DNA damage response (DDR), which includes DNA repair and cell cycle checkpoints activation, leads to radioresistance and limits radiotherapy efficacy in HCC patients. However, the underlying mechanism have not been clearly understood. Methods We obtained 7 pairs of HCC tissues and corresponding non-tumor tissues, and UBE2T was identified as one of the most upregulated genes. The radioresistant role of UBE2T was examined by colony formation assays in vitro and xenograft tumor models in vivo. Comet assay, cell cycle flow cytometry and γH2AX foci measurement were used to investigate the mechanism by which UBE2T mediating DDR. Chromatin fractionation and immunofluorescence staining were used to assess cell cycle checkpoint kinase 1(CHK1) activation. Finally, we analyzed clinical data from HCC patients to verify the function of UBE2T. Results Here, we found that ubiquitin-conjugating enzyme E2T (UBE2T) was upregulated in HCC tissues, and the HCC patients with higher UBE2T levels exhibited poorer outcomes. Functional studies indicated that UBE2T increased HCC radioresistance in vitro and in vivo. Mechanistically, UBE2T-RNF8, was identified as the E2-E3 pair, physically bonded with and monoubiquitinated histone variant H2AX/γH2AX upon radiation exposure. UBE2T-regulated H2AX/γH2AX monoubiquitination facilitated phosphorylation of CHK1 for activation and CHK1 release from the chromatin to cytosol for degradation. The interruption of UBE2T-mediated monoubiquitination on H2AX/γH2AX, including E2-enzyme-deficient mutation (C86A) of UBE2T and monoubiquitination-site-deficient mutation (K119/120R) of H2AX, cannot effectively activate CHK1. Moreover, genetical and pharmacological inhibition of CHK1 impaired the radioresistant role of UBE2T in HCC. Furthermore, clinical data suggested that the HCC patients with higher UBE2T levels exhibited worse response to radiotherapy. Conclusion Our results revealed a novel role of UBE2T-mediated H2AX/γH2AX monoubiquitination on facilitating cell cycle arrest activation to provide sufficient time for radiation-induced DNA repair, thus conferring HCC radioresistance. This study indicated that disrupting UBE2T-H2AX-CHK1 pathway maybe a promising potential strategy to overcome HCC radioresistance.

LPCAT1 overexpression promotes the progression of hepatocellular carcinoma

“…Additionally, the cell cycle checkpoint is verified to be one of the most important cell cycle regulatory mechanisms [ 56 ]. Nonetheless, dysregulation of the cell cycle checkpoint might lead to radio resistance of HCC cells, thus causing unfavourable prognosis in HCC patients [ 57 ]. Therefore, the upregulated LPCAT1 CEGs might induce abnormal regulation of the cell cycle and promote the development and deterioration of HCC.…”

UBE2T knockdown inhibits cell growth and metastasis of breast cancer through Wnt/β-catenin pathway

“…Interest in nding useful biomarkers for diagnosis and treatment of breast cancer has been accumulating. Increasing data indicated that aberrant UBE2T expression has serve important roles in almost all cell biological behaviors, including growth, cell cycle, apoptosis, differentiation, apoptosis and metastasis (14)(15)(16)(17). However, little is known about the function of UBE2T in breast cancer.…”

NEDD4L-Induced Ubiquitination Mediated UBE2T Degradation Inhibits Progression of Lung Adenocarcinoma Via PI3K-AKT Signaling

“…NEDD4L triggers the degradation of certain proteins involved in cancer progression, most of which attributed to its E3 ubiquitin ligase function [16,20,35]. Meanwhile, overexpression of UBE2T has been found in a variety type of cancers.…”

“…On the one hand, UBE2T could promote gastric cancer cell progression via hyperactivating the Wnt/β-catenin pathway through the ubiquitination and degradation of RACK1 [16]. On the other hand, UBE2T also could mediate H2AX/γH2AX monoubiquitylation on facilitating cell cycle arrest activation to provide su cient time for radiationinduced DNA repair, thus conferring hepatocellular carcinoma radio-resistance [20]. Consistently, UBE2T was overexpressed and associated with poor prognosis in gastric cancer [16], hepatocellular carcinoma [20], osteosarcoma [17] and breast cancer [15].…”

“…On the other hand, UBE2T also could mediate H2AX/γH2AX monoubiquitylation on facilitating cell cycle arrest activation to provide su cient time for radiationinduced DNA repair, thus conferring hepatocellular carcinoma radio-resistance [20]. Consistently, UBE2T was overexpressed and associated with poor prognosis in gastric cancer [16], hepatocellular carcinoma [20], osteosarcoma [17] and breast cancer [15]. Recently, several lines of investigation revealed that UBE2T promoted proliferation and EMT by ubiquitination-mediated FOXO1 degradation and Wnt/βcatenin signaling pathway activation in NSCLC cells [13,18].…”