Modulation of myocardin function by the ubiquitin E3 ligase UBR

Guoqing Hu, Xiaobo Wang, Darren N. Saunders, Michelle Henderson, Amanda J. Russell, B. Paul Herring, Jiliang Zhou

Research output: Contribution to journalArticle

26 Citations (Scopus)

Abstract

Fully differentiated mature smooth muscle cells (SMCs) are characterized by the presence of a unique repertoire of smooth muscle-specific proteins. Although previous studies have shown myocardin to be a critical transcription factor for stimulating expression of smooth muscle-specific genes, the mechanisms regulating myocardin activity are still poorly understood. We used a yeast two-hybrid screen with myocardin as bait to search for factors that may regulate the transcriptional activity of the myocardin. From this screen we identified a HECT domain-containing protein UBR5 (ubiquitin protein ligase E3 component n-recognin 5) as a myocardin-binding protein. Previous studies have shown that HECT domain-containing proteins are ubiquitin E3 ligases that play an important role in protein degradation. UBR5 has, however, also been shown to regulate transcription independent of its E3 ligase activity. In the current study we demonstrated that UBR5 localized in the nuclei of SMCs and forms a complex with myocardin in vivo and in vitro. We also show that UBR5 specifically enhanced trans-activation of smooth muscle-specific promoters by the myocardin family of proteins. In addition, UBR5 significantly augmented the ability of myocardin to induce expression of endogenous SMC marker genes independent on its E3 ligase function. Conversely, depletion of endogenous UBR5 by small interfering RNA in fibroblast cells attenuated myocardin-induced smooth muscle-specific gene expression, and UBR5 knockdown in SMCs resulted in down-regulation of smooth muscle-specific genes. Furthermore, we found that UBR5 can attenuate myocardin protein degradation resulting in increased myocardin protein expression without affecting myocardin mRNA expression. The effects of UBR5 on myocardin requires only the HECT and UBR1 domains of UBR5. This study reveals an unexpected role for the ubiquitin E3 ligase UBR5 as an activator of smooth muscle differentiation through its ability to stabilize myocardin protein.

Original languageEnglish (US)
Pages (from-to)11800-11809
Number of pages10
JournalJournal of Biological Chemistry
Volume285
Issue number16
DOIs
StatePublished - Apr 16 2010

Fingerprint

Ubiquitin-Protein Ligases
Modulation
Muscle
Smooth Muscle
Smooth Muscle Myocytes
Proteins
Genes
Cells
myocardin
Proteolysis
Degradation
Muscle Proteins
Transcription
Fibroblasts
Gene expression
Yeast
Muscle Cells
Small Interfering RNA

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

Cite this

Hu, G., Wang, X., Saunders, D. N., Henderson, M., Russell, A. J., Herring, B. P., & Zhou, J. (2010). Modulation of myocardin function by the ubiquitin E3 ligase UBR. Journal of Biological Chemistry, 285(16), 11800-11809. https://doi.org/10.1074/jbc.M109.079384

Modulation of myocardin function by the ubiquitin E3 ligase UBR. / Hu, Guoqing; Wang, Xiaobo; Saunders, Darren N.; Henderson, Michelle; Russell, Amanda J.; Herring, B. Paul; Zhou, Jiliang.

In: Journal of Biological Chemistry, Vol. 285, No. 16, 16.04.2010, p. 11800-11809.

Research output: Contribution to journalArticle

Hu, G, Wang, X, Saunders, DN, Henderson, M, Russell, AJ, Herring, BP & Zhou, J 2010, 'Modulation of myocardin function by the ubiquitin E3 ligase UBR', Journal of Biological Chemistry, vol. 285, no. 16, pp. 11800-11809. https://doi.org/10.1074/jbc.M109.079384
Hu G, Wang X, Saunders DN, Henderson M, Russell AJ, Herring BP et al. Modulation of myocardin function by the ubiquitin E3 ligase UBR. Journal of Biological Chemistry. 2010 Apr 16;285(16):11800-11809. https://doi.org/10.1074/jbc.M109.079384
Hu, Guoqing ; Wang, Xiaobo ; Saunders, Darren N. ; Henderson, Michelle ; Russell, Amanda J. ; Herring, B. Paul ; Zhou, Jiliang. / Modulation of myocardin function by the ubiquitin E3 ligase UBR. In: Journal of Biological Chemistry. 2010 ; Vol. 285, No. 16. pp. 11800-11809.
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