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Graduate Institute of Biomedical Sciences



劉世東(Shih-Tung Liu


LabMolecular Genetic Laboratory


University/NationUniversity of California, Berkeley, USA

Tel: (03)2118800 ext.


Research websitehttp://www.cgu.edu.tw/DMI/teacher/liuSTfront.htm

Research interests:

Molecular Interactions of Epstein-Barr virus Capsid Proteins

The capsid of herpesviruses, which comprises major and minor capsid proteins, has a common icosahedral structure with 162 capsomers. An electron microscopic study shows that Epstein-Barr virus (EBV) capsids in the nucleus are immunolabeled by anti-BDLF1 and anti-BORF1 antibodies, indicating that BDLF1 and BORF1 are the minor capsid proteins of EBV. Crosslinking and electrophoresis studies of purified BDLF1 and BORF1 revealed that these two proteins form a triplex that is similar to that formed by the minor capsids proteins, VP19C and VP23, of herpes simplex virus type 1 (HSV-1). Although the interaction between VP23, a homolog of BDLF1, and the major capsid protein, VP5, could not be verified biochemically in earlier studies, the interaction between BDLF1 and the EBV major capsid protein, VCA, can be confirmed by GST-pull-down assay and coimmunoprecipitation. Additionally, in HSV-1, VP5 interacts with only the middle region of VP19C; in EBV, VCA interacts with both the N-terminal and the middle regions of BORF1, a homolog of VP19C, revealing that the proteins in the EBV triplex interact with the major capsid protein differently from those in HSV-1. A GST-pull-down study also identifies the oligomerization domains in VCA and the dimerization domain in BDLF1. The results presented herein reveal how the EBV capsid proteins interact, and thereby improve our understanding of the capsid structure of the virus.

Characterization and Intracellular Trafficking of Epstein-Barr virus BBLF1, a Protein involved in virion Maturation.

Epstein-Barr virus (EBV) BBLF1 shares 13 to 15% amino acid sequence identities with the herpes simplex virus 1 UL11 and cytomegalovirus UL99 tegument proteins, which are involved in the final envelopment during viral maturation. This study demonstrates that BBLF1 is a myristoylated and palmitoylated protein, as are UL11 and UL99. Myristoylation of BBLF1 both facilitates its membrane anchoring and stabilizes it. BBLF1 is shown to localize to the trans-Golgi network (TGN) along with gp350/220, a site where final envelopment of EBV particles takes place. The localization of BBLF1 at the TGN requires myristoylation and two acidic clusters, which interact with PACS-1, a cytosolic protein, to mediate retrograde transport from the endosomes to the TGN. Knockdown of the expression of BBLF1 during EBV lytic replication reduces the production of virus particles, demonstrating the requirement of BBLF1 to achieve optimal production of virus particles. BBLF1 is hypothesized to facilitate the budding of tegumented capsid into glycoprotein-embedded membrane during viral maturation.

MCAF1 and synergistic activation of the transcription of Epstein–Barr virus lytic genes by Rta and Zta

Epstein–Barr virus (EBV) expresses two transcription factors, Rta and Zta, during the immediate-early stage of the lytic cycle. The two proteins often collaborate to activate the transcription of EBV lytic genes synergistically. This study demonstrates that Rta and Zta form a complex via an intermediary protein, MCAF1, on Zta response element (ZRE) in vitro. The interaction among these three proteins in P3HR1 cells is also verified via coimmunoprecipitation, CHIP analysis and confocal microscopy. The interaction between Rta and Zta in vitro depends on the region between amino acid 562 and 816 in MCAF1. In addition, overexpressing MCAF1 enhances and introducing MCAF1 siRNA into the cells markedly reduces the level of the synergistic activation in 293T cells. Moreover, the fact that the synergistic activation depends on ZRE but not on Rta response element (RRE) originates from the fact that Rta and Zta are capable of activating the BMRF1 promoter synergistically after an RRE but not ZREs in the promoter are mutated. The binding of Rta–MCAF1–Zta complex to ZRE but not RRE also explains why Rta and Zta do not use RRE to activate transcription synergistically. Importantly, this study elucidates the mechanism underlying synergistic activation, which is important to the lytic development of EBV.

Activation of the Promoter of the FengycinSynthetase Operon by the UP Element

Bacillus subtilis F29-3 produces an antifungal peptidic antibiotic that is synthesized nonribosomally by fengycinsynthetases. Our previous work established that the promoter of the fengycinsynthetase operon is located 86 nucleotides upstream of the translational initiation codon of fenC. This investigation involved transcriptional fusions with a DNA fragment that contains the region between positions -105 and +80 and determined that deleting the region between positions -55 and -42 reduces the promoter activity by 64.5%. Transcriptional fusions in the B. subtilis DB2 chromosome also indicated that mutating the sequence markedly reduces the promoter activity. An in vitro transcription analysis confirmed that the transcription is inefficient when the sequence in this region is mutated. Electrophoretic mobility shift and footprinting analyses demonstrated that the C-terminal domain of the RNA polymerase alpha subunit binds to the region between positions -55 and -39. These results indicated that the sequence is an UP element. Finally, this UP element is critical for the production of fengycin, since mutating the UP sequence in the chromosome of B. subtilis F29-3 reduces the transcription of the fen operon by 85% and prevents the cells from producing enough fengycin to suppress the germination of Paecilomycesvariotii spores on agar plates.



1.          C.-Y. Wu, C.-L. Chen, Y.-H. Lee, Y.-C. Cheng, Y.-C. Wu, H.-Y. Shu, F. Götz, and S.-T. Liu. 2007. Nonribosomal Synthesis of Fengycin on an Enzyme Complex Formed by FengycinSynthetases. J. Biol. Chem.282:5608-5616.

2.          Y.-F. Chiu, C.-P. Tung, Y.-H. Lee, W.-H. Wang, C. Li, J.-Y. Hung, C.-Y. Wang, and S.-T. Liu. 2007. A Comprehensive Library of Mutations of Epstein-Barr Virus. J. Gen. Virol.88:2463-2472.

3.          M.-H. Lin, and S.-T. Liu. 2008. Stabilization of pSW100 from Pantoeastewartii by F conjugation system. J. Bacteriol.190:3681-3689.

4.          L.-K. Chang, S.-T. Liu, C.-W. Kuo, W.-H. Wang, J.-Y. Chuang, E. Bianchi, and Y.-R. Hong. 2008. Enhancement of Transactivation Activity of Rta of Epstein-Barr Virus by RanBPM. J. Mol. Biol. 379:231-242.

5.          Y.-H. Lee, Y.-F. Chiu, W.-H. Wang, L.-K. Chang, and S.-T. Liu. 2008. Activation of the ERK signal transduction pathway by Epstein-Barr virus immediate-early protein Rta. J. Gen. Virol.89(10):2437-2446.

6.          W.-J. Ke, B.-Y. Chang, T.-P. Lin, and S.-T. Liu. 2009. Activation of the Promoter of the FengycinSynthetase Operon by the UP Element. J. Bacteriol. 191(14):4615-4623.

7.          C.-Y. Yen, M.-C. Lu, C.-C. Tzeng, J.-Y. Huang, H.-W. Chang, R.-S. Chen, S.-Y. Liu, S.-T. Liu, B. Shieh, and C. Li. 2009. Detection of EBV Infection and Gene Expression in Oral Cancer from Patients in Taiwan by Microarray Analysis. J. Biomed Biotechnol. Volume 2009, Article ID 904589, 15 pages, doi:10.1155/2009/904589.

8.          L.-K. Chang, J.-Y. Chuang, MitsuyoshiNakao, and S.-T. Liu. 2010. MCAF1 and synergistic activation of the transcription of Epstein-Barr virus lytic genes by Rta and Zta. Nucleic Acids Res. 38(14):4687-4700.doi:10.1093/nar/gkq243.

9.          Y.-C. Wu, and S.-T. Liu. 2010. A Sequence That Affects the Copy Number and Stability of pSW200 and ColE1. J. Bacteriol. 192(14):3654-3660.

10.      W.-H. Wang, L.-K. Chang, and S.-T. Liu. 2011. Molecular interactions of Epstein-Barr virus capsid proteins. J. Virol.85(4):1615-1624.

11.      M.-H. Lin, F.-R. Chang, M.-Y. Hua, Y.-C. Wu, and S.-T. Liu. 2011. Inhibitory effects of 1,2,3,4,6-penta-O-galloyl-β-D-glucopyranose on biofilm formation by Staphylococcus aureus. Antimicrob. Agents Ch.55(3):1021-1027.

12.      C.-W. Kuo, W.-H. Wang, and S.-T. Liu. 2011. Mapping Signals that Are Important for Nuclear and Nucleolar Localiztion in MCRS2. Mol. Cells31(6):547-552.

13.      C.-P. Tung, F.-R. Chang, Y.-C. Wu, D.-W. Chuang, A. Hunyadi, and S.-T. Liu. 2011. Inhibition of the Epstein-Barr virus lytic cycle by protoapigenone. J. Gen. Virol.92(8):1760-1768.

14.      Y.-F. Chiu, B. Sugden, P.-J. Chang, L.-W. Chen, Y.-J. Lin, Y.-C. Lan, C.-H. Lai, J.-Y. Liou, S.-T. Liu, and C.-H. Hung. 2012. Characterization and Intracellular Trafficking of Epstein-Barr Virus BBLF1, a Protein Involved in Virion Maturation. J. Virol.86(18):9647-9655.


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