The Sumo-targeted ubiquitin ligase RNF4 regulates the localization and function of the HTLV-1 oncoprotein Tax

Blood. 2012 Feb 2;119(5):1173-81. doi: 10.1182/blood-2011-06-358564. Epub 2011 Nov 21.


The Really Interesting New Gene (RING) Finger Protein 4 (RNF4) represents a class of ubiquitin ligases that target Small Ubiquitin-like Modifier (SUMO)-modified proteins for ubiquitin modification. To date, the regulatory function of RNF4 appears to be ubiquitin-mediated degradation of sumoylated cellular proteins. In the present study, we show that the Human T-cell Leukemia Virus Type 1 (HTLV-1) oncoprotein Tax is a substrate for RNF4 both in vivo and in vitro. We mapped the RNF4-binding site to a region adjacent to the Tax ubiquitin/SUMO modification sites K280/K284. Interestingly, RNF4 modification of Tax protein results in relocalization of the oncoprotein from the nucleus to the cytoplasm. Overexpression of RNF4, but not the RNF4 RING mutant, resulted in cytoplasmic enrichment of Tax. The RNF4-induced nucleus-to-cytoplasm relocalization was associated with increased NF-κB-mediated and decreased cAMP Response Element-Binding (CREB)-mediated Tax activity. Finally, depletion of RNF4 by RNAi prevented the DNA damage-induced nuclear/cytoplasmic translocation of Tax. These results provide important new insight into STUbL-mediated pathways that regulate the subcellular localization and functional dynamics of viral oncogenes.

Publication types

  • Research Support, American Recovery and Reinvestment Act
  • Research Support, N.I.H., Extramural

MeSH terms

  • Active Transport, Cell Nucleus / genetics
  • Cell Nucleus / metabolism
  • Cells, Cultured
  • DNA Damage / genetics
  • DNA Damage / physiology
  • Gene Expression / physiology
  • Gene Products, tax / genetics
  • Gene Products, tax / metabolism*
  • Gene Products, tax / physiology*
  • HEK293 Cells
  • Humans
  • Nuclear Proteins / genetics
  • Nuclear Proteins / metabolism
  • Nuclear Proteins / physiology*
  • Oncogene Proteins / metabolism
  • Oncogene Proteins / physiology
  • Protein Binding
  • Protein Transport
  • SUMO-1 Protein / metabolism
  • Tissue Distribution
  • Transcription Factors / genetics
  • Transcription Factors / metabolism
  • Transcription Factors / physiology*
  • Transfection
  • Ubiquitination / physiology


  • Gene Products, tax
  • Nuclear Proteins
  • Oncogene Proteins
  • RNF4 protein, human
  • SUMO-1 Protein
  • Transcription Factors
  • tax protein, Human T-lymphotrophic virus 1