Functional Dissection of Latency-Associated Nuclear Antigen 1 of Kaposi's Sarcoma-Associated Herpesvirus Involved in Latent DNA Replication and Transcription of Terminal Repeats of the Viral Genome

Latency-associated nuclear antigen 1 (LANA1) of Kaposi's sarcoma-associated herpesvirus (KSHV) is implicated in the maintenance of the viral genome during latent infection. LANA1 colocalizes with KSHV episomes on the host chromosome and mediates their maintenance by attaching these viral structures to host chromosomes. Data from long-term selection of drug resistance in cells conferred by plasmids containing the terminal repeat (TR) sequence of KSHV revealed that KSHV TRs and LANA1 act as cis and trans elements of viral latent replication, respectively. In this study, we further characterized the cis- and trans-acting elements of KSHV latent replication by using a transient replication assay with a methylation-sensitive restriction enzyme, DpnI. Transient reporter and replication assays disclosed that the orientation and basal transcriptional activity of TR constructs did not significantly affect the efficiency of replication. However, at least two TR units were necessary for efficient replication. The N-terminal 90 amino acids comprising the chromosome-binding domain of LANA1 were required for the mediation of LANA1 C-terminal DNA-binding and dimerization domains to support the transient replication of KSHV TRs. LANA1 interacted with components of the origin recognition complexes (ORCs), similar to Epstein-Barr virus nuclear antigen 1. Our data suggest that LANA1 recruits ORCs to KSHV TRs for latent replication of the viral genome.