Targeting of the gene product encoded by ORF UL56 of human cytomegalovirus into viral replication centers

The highly conserved DNA-binding protein pUL56 of human cytomegalovirus (HCMV) was found to be predominantly localized throughout the nucleus as well as in viral replication centers of infected cells. The latter localization was abolished by phosphono acetic acid, an inhibitor of viral DNA replication. Immunofluorescence revealed that pUL56 co-localized in replication centers alongside pUL112–113 and pUL44 at late times of infection. By co-immunoprecipitations, a direct interaction with pUL44, a protein of the replication fork, was detected. These results showed for the first time that HCMV pUL56 is localized in viral replication centers, implicating that DNA replication is coupled with packaging.