Transcription factor single-minded 2 (SIM2) is ubiquitinated by the RING-IBR-RING-type E3 ubiquitin ligases

Michiyo Okui, Akiko Yamaki, Atsushi Takayanagi, Jun Kudoh, Nobuyoshi Shimizu, Yoshiko Shimizu

Research output: Contribution to journalArticlepeer-review

17 Citations (Scopus)


Human single-minded 2 (SIM2) is a member of the basic helix-loop-helix/Per- Arnt-Sim (bHLH/PAS) family of transcription factors and is associated with the etiology of Down syndrome phenotype. Here, we examined a possibility of the post-translational modification of SIM2 protein by transfecting various expression constructs followed by the analysis with immunoprecipitation and Western blotting. In fact, transient expression of SIM2 cDNA in HEK293 cells revealed poly-ubiquitination of SIM2 protein. In the stable transfectants, a proteasome inhibitor MG132 protected the poly-ubiquitinated SIM2 protein from degradation. Furthermore, in the cells co-transfected with SIM2 and each of four different E3 ubiquitin ligases, SIM2 was immunoprecipitated with the RING-IBR-RING-type E3 ubiquitin ligases, Parkin and HHARI, but it was not immunoprecipitated with other E3 ligases, such as one RING-type Siah-1 and the PHD type AIRE. A series of deletion constructs revealed that Parkin actually binds to SIM2 with the IBR (294-377)-RING2 (378-465) domains and that the sites for poly-ubiquitination of SIM2 reside within the PAS1-PAS2 region (aa 141-289). We postulated that transcription factor SIM2 and E3 ubiquitin ligase Parkin may interact each other to play an important physiological role in the brain development which is controlled by ubiquitination.

Original languageEnglish
Pages (from-to)220-228
Number of pages9
JournalExperimental Cell Research
Issue number1
Publication statusPublished - 2005 Sept 10


  • Down syndrome
  • Human homologue of Drosophila ariadine
  • Parkin
  • Proteasome
  • RING-type E3 ubiquitin ligase
  • SIM2
  • Single-minded 2
  • Transcription factor
  • Ubiquitination
  • bHLH-PAS family

ASJC Scopus subject areas

  • Cell Biology


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