Differential Degradation of TRA2A and PYCR2 Mediated by Ubiquitin E3 Ligase E4B

Yao Lu; Bo Jiang; Kangli Peng; Shasha Li; Xiangnan Liu; Bufan Wang; Yuntian Chen; Tiepeng Wang; Bo Zhao

doi:10.3389/fcell.2022.833396

Differential Degradation of TRA2A and PYCR2 Mediated by Ubiquitin E3 Ligase E4B

Front Cell Dev Biol. 2022 May 20:10:833396. doi: 10.3389/fcell.2022.833396. eCollection 2022.

Authors

Yao Lu¹, Bo Jiang^{2

3}, Kangli Peng¹, Shasha Li¹, Xiangnan Liu¹, Bufan Wang¹, Yuntian Chen⁴, Tiepeng Wang⁵, Bo Zhao¹

Affiliations

¹ Engineering Research Center of Cell and Therapeutic Antibody, Ministry of Education, and School of Pharmacy, Shanghai Jiao Tong University, Shanghai, China.
² Department of Hand and Foot Surgery, The Second Affiliated Hospital of Soochow University, Suzhou, China.
³ State Key Laboratory of Radiation Medicine and Protection, Soochow University, Suzhou, China.
⁴ Department of Respiratory and Critical Care Medicine, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.
⁵ National Laboratory of Biomacromolecules, Chinese Academy of Sciences Center for Excellence in Biomacromolecules, Institute of Biophysics, Beijing, China.

Abstract

E4B belongs to the U-box E3 ligase family and functions as either an E3 or an E4 enzyme in protein ubiquitination. Transformer2A (TRA2A) and Pyrroline-5-carboxylate reductase 2 (PYCR2) are related to cancer development and are overexpressed in many cancer cells. The degradation of TRA2A and PYCR2 mediated by the ubiquitin-proteasome system (UPS) has not been reported. This study validated that E4B could ubiquitinate TRA2A and PYCR2 as an E3 ligase both in vitro and in the HEK293 cells. E4B mediated the degradation by forming K11- and K48- linked polyubiquitin chains on TRA2A and PYCR2, respectively. E4B regulated the alternative splicing function of TRA2A and affected RSRC2 transcription in the HEK293 cells. Although E4B is highly expressed, it hardly degrades TRA2A and PYCR2 in hepatocellular carcinoma (HCC) cells, suggesting other mechanisms exist for degradation of TRA2A and PYCR2 in the HCC cells. We finally reported that E4B interacted with substrates via its variable region.

Keywords: E4B; PYCR2; TRA2A; degradation; ubiquitin; ubiquitination.