title: Phosphorylation of hepatitis B virus Cp at Ser87 facilitates core assembly.
abstract: Protein-protein interactions can be regulated by protein modifications such as phosphorylation. Some of the phosphorylation sites (Ser155, Ser162 and Ser170) of HBV (hepatitis B virus) Cp have been discovered and these sites are implicated in the regulation of viral genome encapsidation, capsid localization and nucleocapsid maturation. In the present report, the dimeric form of HBV Cp was phosphorylated by PKA (protein kinase A), but not by protein kinase C in vitro, and the phosphorylation of dimeric Cp facilitated HBV core assembly. Matrix-assisted laser-desorption ionization-time-of-flight analysis revealed that the HBV Cp was phosphorylated at Ser87 by PKA. This was further confirmed using a mutant HBV Cp with S87G mutation. The S87G mutation inhibited the phosphorylation and, as a result, the in vitro HBV core assembly was not facilitated by PKA. In addition, when either pCMV/FLAG-Core(WT) or pCMV/FLAG-Core(S87G) was transfected into HepG2 cells, few mutant Cps (S87G) assembled into capsids compared with the wild-type (WT) Cps, although the same level of total Cps was expressed in both cases. In conclusion, PKA facilitates HBV core assembly through phosphorylation of the HBV Cp at Ser87.
authors.affiliation: School of Biological Sciences, Seoul National University, Shillim-dong, Seoul 151-742, South Korea.
authors.forename: Hee Yong
authors.initials: HY
authors.lastname: Kang
authors.forename: Seungkeun
authors.initials: S
authors.lastname: Lee
authors.forename: Sung Gyoo
authors.initials: SG
authors.lastname: Park
authors.forename: Jaehoon
authors.initials: J
authors.lastname: Yu
authors.forename: Youngsoo
authors.initials: Y
authors.lastname: Kim
authors.forename: Guhung
authors.initials: G
authors.lastname: Jung
mesh_terms: D000595:Amino Acid Sequence; D036022:Capsid Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D045744:Cell Line, Tumor; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D006515:Hepatitis B virus / Q000737:chemistry* / Q000145:classification / Q000378:metabolism* / Q000648:ultrastructure; D006801:Humans; D007700:Kinetics; D046529:Microscopy, Electron, Transmission; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011485:Protein Binding; D012694:Serine / Q000235:genetics / Q000378:metabolism*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D020349:Surface Plasmon Resonance; D019065:Virus Assembly
chemical_list: D036022:Capsid Proteins; D012694:Serine; D017868:Cyclic AMP-Dependent Protein Kinases