Human Cytomegalovirus Terminase: Insights into structure-function relationships

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Human cytomegalovirus (HCMV) belongs to the ß-herpesviruses and is characterized by its narrow host range. HCMV seroprevalence is more than 50% worldwide, and HCMV infection leads to serious inflammatory disease in immunocompromised patients, e.g. transplant recipients and AIDS patients. Currently available drugs have limited effectiveness and lead to resistance. Key steps in HCMV maturation are DNA replication and packaging into capsids, which require cleavage of concatenated DNA into unit-length genomes. This process is not found in mammalian cells and therefore a promising target for anti-HCMV therapy. We have demonstrated that the HCMV terminase, consisting of two subunits, pUL56 and pUL89, is involved in the cleavage process. Recently we identified in vitro two potential DNA-binding domains in the C-terminal part of terminase subunit pUL56 and one in the N-terminal part of subunit pUL89. A requirement for the function is the interaction of the terminase subunits. In this project, these DNA-binding domains as well as the interaction domain of pUL89 will be validated by the generation of different HCMV deletion mutants. The mutant viruses will be characterized concerning their growth kinetics, viral particle formation and their DNA binding ability. The proposed work will lead to a consistent model of HCMV DNA replication and will be important for the development of highly specific antivirals targeting the essential domains of the terminase subunits.