title: Apoptin T108 phosphorylation is not required for its tumor-specific nuclear localization but partially affects its apoptotic activity.
abstract: Apoptin, a chicken anemia virus-encoded protein, induces apoptosis in human tumor cells but not in normal cells. In addition, Apoptin also exhibits tumor-specific nuclear localization and tumor-specific phosphorylation on threonine 108 (T108). Here, we studied the effects of T108 phosphorylation on the tumor-specific nuclear localization and apoptotic activity of Apoptin. We first showed that a hemagglutinin (HA)-tagged Apoptin, but not the green fluorescent protein-fused Apoptin used in many previous studies, exhibited the same intracellular distribution pattern as native Apoptin. We then made and analyzed an HA-Apoptin mutant with its T108 phosphorylation site abolished. We found that Apoptin T108 phosphorylation is not required for its tumor-specific nuclear localization and abolishing the T108 phosphorylation of Apoptin does affect its apoptotic activity in tumor cells but only partially. Our results support the previous finding that Apoptin contains two distinct apoptosis domains located separately at the N- and C-terminal regions and suggest that the T108 phosphorylation may only be required for the apoptotic activity mediated through the C-terminal apoptosis domain.
authors.affiliation: Faculty of Biomedical Science and Environmental Biology, Kaohsiung Medical University, No. 100, Shih-Chuan 1st Road, Kaohsiung 807, Taiwan, ROC.
authors.forename: Yen-Hsien
authors.initials: YH
authors.lastname: Lee
authors.forename: Chih-Mei
authors.initials: CM
authors.lastname: Cheng
authors.forename: Yung-Fu
authors.initials: YF
authors.lastname: Chang
authors.forename: Ting-Yi
authors.initials: TY
authors.lastname: Wang
authors.forename: Chung-Yee
authors.initials: CY
authors.lastname: Yuo
mesh_terms: D019943:Amino Acid Substitution / Q000235:genetics; D017209:Apoptosis / Q000235:genetics / Q000502:physiology*; D036022:Capsid Proteins / Q000235:genetics / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism*; D049452:Green Fluorescent Proteins; D006367:HeLa Cells; D006388:Hemagglutinins / Q000378:metabolism; D006801:Humans; D009363:Neoplasm Proteins / Q000378:metabolism*; D010766:Phosphorylation; D017434:Protein Structure, Tertiary / Q000235:genetics; D013912:Threonine / Q000235:genetics / Q000378:metabolism*
chemical_list: D036022:Capsid Proteins; D006388:Hemagglutinins; D009363:Neoplasm Proteins; C091717:VP3 protein, Chicken anemia virus; D049452:Green Fluorescent Proteins; D013912:Threonine