title: The human cytomegalovirus UL51 protein is essential for viral genome cleavage-packaging and interacts with the terminase subunits pUL56 and pUL89.
abstract: Cleavage of human cytomegalovirus (HCMV) genomes as well as their packaging into capsids is an enzymatic process mediated by viral proteins and therefore a promising target for antiviral therapy. The HCMV proteins pUL56 and pUL89 form the terminase and play a central role in cleavage-packaging, but several additional viral proteins, including pUL51, had been suggested to contribute to this process, although they remain largely uncharacterized. To study the function of pUL51 in infected cells, we constructed HCMV mutants encoding epitope-tagged versions of pUL51 and used a conditionally replicating virus (HCMV-UL51-ddFKBP), in which pUL51 levels could be regulated by a synthetic ligand. In cells infected with HCMV-UL51-ddFKBP, viral DNA replication was not affected when pUL51 was knocked down. However, no unit-length genomes and no DNA-filled C capsids were found, indicating that cleavage of concatemeric HCMV DNA and genome packaging into capsids did not occur in the absence of pUL51. pUL51 was expressed mainly with late kinetics and was targeted to nuclear replication compartments, where it colocalized with pUL56 and pUL89. Upon pUL51 knockdown, pUL56 and pUL89 were no longer detectable in replication compartments, suggesting that pUL51 is needed for their correct subnuclear localization. Moreover, pUL51 was found in a complex with the terminase subunits pUL56 and pUL89. Our data provide evidence that pUL51 is crucial for HCMV genome cleavage-packaging and may represent a third component of the viral terminase complex. Interference with the interactions between the terminase subunits by antiviral drugs could be a strategy to disrupt the HCMV replication cycle.
authors.affiliation: Institute for Virology, Hannover Medical School, Hannover, Germany.
authors.forename: Eva Maria
authors.initials: EM
authors.lastname: Borst
authors.forename: Jennifer
authors.initials: J
authors.lastname: Kleine-Albers
authors.forename: Ildar
authors.initials: I
authors.lastname: Gabaev
authors.forename: Marina
authors.initials: M
authors.lastname: Babic
authors.forename: Karen
authors.initials: K
authors.lastname: Wagner
authors.forename: Anne
authors.initials: A
authors.lastname: Binz
authors.forename: Inga
authors.initials: I
authors.lastname: Degenhardt
authors.forename: Markus
authors.initials: M
authors.lastname: Kalesse
authors.forename: Stipan
authors.initials: S
authors.lastname: Jonjic
authors.forename: Rudolf
authors.initials: R
authors.lastname: Bauerfeind
authors.forename: Martin
authors.initials: M
authors.lastname: Messerle
mesh_terms: D002478:Cells, Cultured; D003587:Cytomegalovirus / Q000201:enzymology / Q000502:physiology*; D004279:DNA, Viral / Q000378:metabolism*; D004706:Endodeoxyribonucleases / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D006868:Hydrolysis; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism*; D015678:Viral Structural Proteins / Q000235:genetics / Q000378:metabolism*; D019065:Virus Assembly
chemical_list: D004279:DNA, Viral; C090238:UL56 protein, cytomegalovirus; C436448:UL89 protein, Cytomegalovirus; D014764:Viral Proteins; D015678:Viral Structural Proteins; D004706:Endodeoxyribonucleases; C030894:terminase