Analysis of the interactions of viral and cellular factors with human cytomegalovirus lytic origin of replication, oriLyt.

Human cytomegalovirus transient lytic DNA replication relies on the cis-acting element oriLyt, six viral-encoded core proteins, the proposed DNA replication initiator protein UL84, IE2, IRS1 and the gene products from the UL112/113 loci. In an effort to elucidate cellular and viral-encoded factors that may play a role in oriLyt-dependent replication we used DNA-affinity purification and mass spectrometry to isolate and identify several previously unknown cellular and viral factors that interact with HCMV oriLyt DNA. These proteins include the multifunctional hnRNP-K, BUB3, HMGB1, PTB-1, UL83, UL112/113, and IRS1.

Human cytomegalovirus UL84 oligomerization and heterodimerization domains act as transdominant inhibitors of oriLyt-dependent DNA replication: evidence that IE2-UL84 and UL84-UL84 interactions are required for lytic DNA replication.

Human cytomegalovirus (HCMV) UL84 encodes a 75-kDa protein required for oriLyt-dependent DNA replication and interacts with IE2 in infected and transfected cells. UL84 localizes to the nucleus of transfected and infected cells and is found in viral replication compartments. In transient assays it was shown that UL84 can interfere with the IE2-mediated transactivation of the UL112/113 promoter of HCMV.

Amplification of the Kaposi's sarcoma-associated herpesvirus/human herpesvirus 8 lytic origin of DNA replication is dependent upon a cis-acting AT-rich region and an ORF50 response element and the trans-acting factors ORF50 (K-Rta) and K8 (K-bZIP).

Kaposi's sarcoma-associated herpesvirus (KSHV), also known as human herpesvirus 8 (HHV8), has significant sequence homology to Epstein-Barr virus (EBV). In cell culture, HHV8 is primarily latent, and viral genes associated with lytic replication are not expressed. Two lytic origins of DNA replication (oriLyt) are present within the HHV8 genome and are composed of an AT-rich region adjacent to GC-rich DNA sequences.