Regulation of microtubule dynamics through phosphorylation on stathmin by Epstein-Barr virus kinase BGLF4.
Stathmin is an important microtubule (MT)-destabilizing protein, and its activity is differently attenuated by phosphorylation at one or more of its four phosphorylatable serine residues (Ser-16, Ser-25, Ser-38, and Ser-63). This phosphorylation of stathmin plays important roles in mitotic spindle formation. We observed increasing levels of phosphorylated stathmin in Epstein-Barr virus (EBV)-harboring lymphoblastoid cell lines (LCLs) and nasopharyngeal carcinoma (NPC) cell lines during the EBV lytic cycle. These suggest that EBV lytic products may be involved in the regulation of stathmin phosphorylation. BGLF4 is an EBV-encoded kinase and has similar kinase activity to cdc2, an important kinase that phosphorylates serine residues 25 and 38 of stathmin during mitosis. Using an siRNA approach, we demonstrated that BGLF4 contributes to the phosphorylation of stathmin in EBV-harboring NPC. Moreover, we confirmed that BGLF4 interacts with and phosphorylates stathmin using an in vitro kinase assay and an in vivo two-dimensional electrophoresis assay. Interestingly, unlike cdc2, BGLF4 was shown to phosphorylate non-proline directed serine residues of stathmin (Ser-16) and it mediated phosphorylation of stathmin predominantly at serines 16, 25, and 38, indicating that BGLF4 can down-regulate the activity of stathmin. Finally, we demonstrated that the pattern of MT organization was changed in BGLF4-expressing cells, possibly through phosphorylation of stathmin. In conclusion, we have shown that a viral Ser/Thr kinase can directly modulate the activity of stathmin and this contributes to alteration of cellular MT dynamics and then may modulate the associated cellular processes.
Chen
Po-Wen
PW
Graduate Institute of Microbiology, College of Medicine, National Taiwan University, Taipei 10051, Taiwan.
Lin
Sue-Jane
SJ
Research Center for Emerging Viral Infections and Department of Medical Biotechnology and Laboratory Science, Chang Gung University, Taoyuan 333, Taiwan.
Tsai
Shu-Chun
SC
Graduate Institute of Microbiology, College of Medicine, National Taiwan University, Taipei 10051, Taiwan.
Lin
Jiun-Han
JH
Graduate Institute of Microbiology, College of Medicine, National Taiwan University, Taipei 10051, Taiwan.
Chen
Mei-Ru
MR
Graduate Institute of Microbiology, College of Medicine, National Taiwan University, Taipei 10051, Taiwan.
Wang
Jiin-Tarng
JT
Graduate Institute of Microbiology, College of Medicine, National Taiwan University, Taipei 10051, Taiwan.
Lee
Chung-Pei
CP
Graduate Institute of Microbiology, College of Medicine, National Taiwan University, Taipei 10051, Taiwan.
Tsai
Ching-Hwa
CH
Graduate Institute of Microbiology, College of Medicine, National Taiwan University, Taipei 10051, Taiwan. Electronic address: chtsai@ntu.edu.tw.
D045744:Cell Line, Tumor; D015536:Down-Regulation; D015180:Electrophoresis, Gel, Two-Dimensional; D019084:Fluorescent Antibody Technique, Indirect; D006367:HeLa Cells; D004854:Herpesvirus 4, Human / Q000201:enzymology*; D006801:Humans; D007963:Leukocytes, Mononuclear / Q000378:metabolism; D008870:Microtubules / Q000378:metabolism*; D008938:Mitosis; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics* / Q000502:physiology*; D012694:Serine / Q000737:chemistry; D050777:Stathmin / Q000378:metabolism*; D014162:Transfection; D014764:Viral Proteins / Q000235:genetics* / Q000502:physiology*
D050777:Stathmin; D014764:Viral Proteins; D012694:Serine; C406063:BGLF4 protein, Epstein-Barr virus; D017346:Protein Serine-Threonine Kinases