Kaposi's sarcoma (KS) is a common malignancy in untreated AIDS patients that is caused by the infection of Kaposi's sarcoma-associated herpesvirus (KSHV). KS lesions are characterized by spindle-shaped endothelial cells with infiltration of inflammatory cells and neo-angiogenesis. KSHV commonly establishes default latent infection, but lytic replications occur in a small fraction of cells and play critical roles in KS pathogenesis by serving as a reservoir of infectious virion for persistent infection and inducing continuous paracrine factors for tumor progression. KSHV lytic infection triggers a variety of cellular machinery for replication and remodels cellular transcriptome. Distinct transcriptional patterns are exhibited in the immediate early (IE) and late stages of lytic replication. Previous studies have revealed that multiple pathways activate IE gene expression during lytic infection and reactivation from latency. However, the mechanism of late lytic gene expression regulation has remained largely undefined for a long time. Recently, studies have revealed that both host and viral factors, ORF45-prolonged c-Fos and TATA box binding protein (TBP)-like protein ORF24, are required for late lytic transcription [1, 2].