Liver receptor homolog-1 regulates RING finger protein 138 protein stability

• Main Authors: Jou-Yin Meng, 孟柔吟
• Other Authors: 胡孟君
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/37814890380545477640

碩士 === 國立臺灣大學 === 生理學研究所 === 103 === Liver receptor homolog-1 (LRH-1, NR5A2) is an orphan nuclear receptor, is predominantly expressed in the liver, intestine, pancrease and ovaries. LRH-1 regulates the expression of genes involved in development, metabolism, steroidogenesis and cancinogenesis. We found that LRH-1 reduced the protein level of RNF138 (RING finger protein), and they had interaction in vitro. By protein turnover assay, we found that LRH-1 decreased RNF138 protein stability. In addition, LRH-1 mediated RNF138 protien levels were inhibited by the proteasome inhibitor MG132. These results indicates that LRH-1 may promote RNF138 degradation through proteasome pathway. The GST pull-down experiments showed that LRH-1 interacted with RNF138 N-terminus by DNA binding domain (DBD). It has been reported that the DBD of nuclear receptors has potential RING finger structure. We destroyed the potential loop structure in DBD of LRH-1 by site mutagenesis. These mutants lose the transcriptional activity, but still could reduce RNF138 protein level. It suggested that LRH-1 DBD may not have E3 ligase activity and LRH-1-mediated RNF138 protein reduction was independent of its transactivity. To identify the region responsible for LRH-1 function, a series of LRH-1 truncation constructs were generated. We found that the ligand binding domain (LBD) alone could reduce RNF138 protein level. Together, these results suggested that LRH-1 can reduce RNF138 protein stability that is independent of LRH-1 transcriptional activity and LBD plays an important role in LRH-1-mediated function.