title: Cyclin-dependent kinase 2 phosphorylates s/t-p sites in the hepadnavirus core protein C-terminal domain and is incorporated into viral capsids.
abstract: Phosphorylation of the hepadnavirus core protein C-terminal domain (CTD) is important for viral RNA packaging, reverse transcription, and subcellular localization. Hepadnavirus capsids also package a cellular kinase. The identity of the host kinase that phosphorylates the core CTD or gets packaged remains to be resolved. In particular, both the human hepatitis B virus (HBV) and duck hepatitis B virus (DHBV) core CTDs harbor several conserved serine/threonine-proline (S/T-P) sites whose phosphorylation state is known to regulate CTD functions. We report here that the endogenous kinase in the HBV capsids was blocked by chemical inhibitors of the cyclin-dependent kinases (CDKs), in particular, CDK2 inhibitors. The kinase phosphorylated the HBV CTD at the serine-proline (S-P) sites. Furthermore, we were able to detect CDK2 in purified HBV capsids by immunoblotting. Purified CDK2 phosphorylated the S/T-P sites of the HBV and DHBV CTD in vitro. Inhibitors of CDKs, of CDK2 in particular, decreased both HBV and DHBV CTD phosphorylation in vivo. Moreover, CDK2 inhibitors blocked DHBV CTD phosphorylation, specifically at the S/T-P sites, in a mammalian cell lysate. These results indicate that cellular CDK2 phosphorylates the functionally critical S/T-P sites of the hepadnavirus core CTD and is incorporated into viral capsids.
authors.affiliation: Department of Microbiology and Immunology, The Pennsylvania State University College of Medicine, Hershey, Pennsylvania, USA.
authors.forename: Laurie
authors.initials: L
authors.lastname: Ludgate
authors.forename: Xiaojun
authors.initials: X
authors.lastname: Ning
authors.forename: David H
authors.initials: DH
authors.lastname: Nguyen
authors.forename: Christina
authors.initials: C
authors.lastname: Adams
authors.forename: Laura
authors.initials: L
authors.lastname: Mentzer
authors.forename: Jianming
authors.initials: J
authors.lastname: Hu
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002213:Capsid / Q000737:chemistry; D051357:Cyclin-Dependent Kinase 2 / Q000378:metabolism*; D004372:Ducks; D057809:HEK293 Cells; D056945:Hep G2 Cells; D015613:Hepadnaviridae / Q000378:metabolism*; D006515:Hepatitis B virus / Q000378:metabolism; D006801:Humans; D020128:Inhibitory Concentration 50; D008969:Molecular Sequence Data; D010447:Peptide Hydrolases / Q000378:metabolism; D010766:Phosphorylation; D010770:Phosphotransferases / Q000378:metabolism; D017434:Protein Structure, Tertiary; D011817:Rabbits; D017386:Sequence Homology, Amino Acid; D014758:Viral Core Proteins / Q000737:chemistry
chemical_list: D014758:Viral Core Proteins; D010770:Phosphotransferases; D051357:Cyclin-Dependent Kinase 2; D010447:Peptide Hydrolases