Ubiquitin-dependent and -independent proteasomal degradation of hepatitis B virus X protein

Jung Hwan Kim, Sook Young Sohn, T. S. Benedict Yen, Byung Yoon Ahn

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35 Citations (Scopus)


The hepatitis B virus X protein (HBX) plays key regulatory roles in viral replication and the development of hepatocellular carcinoma. HBX is an unstable protein; its instability is attributed to rapid degradation through the ubiquitin-proteasome pathway. Here, we show that the middle and carboxyl-terminal domains of HBX, independently fused to GFP, render the recombinant proteins susceptible to proteasomal degradation, while the amino-terminal domain has little effect on the ubiquitination or stability of HBX. Mutation of any single or combination of up to five of six lysine residues, all located in the middle and carboxyl-terminal domain, did not prevent HBX from being ubiquitinated, ruling out any specific lysine as the sole site of ubiquitination. Surprisingly, HBX in which all six lysines were mutated and showed no evidence of ubiquitination, was still susceptible to proteasomal degradation. These results suggest that both ubiquitin-dependent and -independent proteasomal degradation processes are operative in HBX turnover.

Original languageEnglish
Pages (from-to)1036-1042
Number of pages7
JournalBiochemical and biophysical research communications
Issue number4
Publication statusPublished - 2008 Feb 22

Bibliographical note

Funding Information:
We are grateful to Dr. J.P. Kim for critical reading of the manuscript. This work was supported by the Korea Research Foundation (KRF-2007-314-C00213), Korea University (K0715471) and the U.S. Department of Veterans Affairs (Merit Review to T.S.B.Y.). J.-H. Kim and S.-Y. Sohn were supported by the BK21 fellowship from the Ministry of Education of Korea.


  • HBV
  • HBX
  • Proteasomal degradation
  • Ub-dependent
  • Ub-independent

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Molecular Biology
  • Cell Biology


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