uAUG-mediated translational initiations are responsible for human mu opioid receptor gene expression

Kyu Young Song*, Chun Sung Kim, Cheol Kyu Hwang, Hack Sun Choi, Ping Yee Law, Li Na Wei, Horace H. Loh

*Corresponding author for this work

Research output: Contribution to journalJournal Article peer-review

9 Scopus citations


Mu opioid receptor (MOR) is the main site of interaction for major clinical analgesics, particularly morphine. MOR expression is regulated at the transcriptional and post-transcriptional levels. However, the protein expression of the MOR gene is relatively low and the translational control of MOR gene has not been well studied. The 5′-untranslated region (UTR) of the human MOR (OPRM1) mRNA contains four upstream AUG codons (uAUG) preceding the main translation initiation site. We mutated the four uAUGs individually and in combination. Mutations of the third uAUG, containing the same open reading frame, had the strongest inhibitory effect. The inhibitory effect caused by the third in-frame uAUG was confirmed by in vitro translation and receptor-binding assays. Toeprinting results showed that OPRM1 ribosomes initiated efficiently at the first uAUG, and subsequently re-initiated at the in-frame #3 uAUG and the physiological AUG site. This re-initiation resulted in negative expression of OPRM1 under normal conditions. These results indicate that re-initiation in MOR gene expression could play an important role in OPRM1 regulation.

Original languageEnglish
Pages (from-to)1113-1124
Number of pages12
JournalJournal of Cellular and Molecular Medicine
Issue number5
StatePublished - 2010
Externally publishedYes


  • Human mu opioid receptor
  • Post-transcriptional regulation
  • UORF


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