Kaposi's sarcoma–associated herpesvirus replication and transcription activator protein activates CD274/PD‐L1 gene promoter

Kaposi's sarcoma–associated herpesvirus (KSHV) is responsible for the pathogenesis of Kaposi's sarcoma, primary effusion lymphoma, and multicentric Castleman disease. The expression of immunosuppressive genes, such as IL‐10 and CD274/PD‐L1 is observed during KSHV‐associated pathogenesis, and the modulation of the host immune system by KSHV contributes to establishing viral persistence in the host. Understanding the mechanism that allows the virus to evade host cell immunity would be helpful in order to develop therapeutic strategies for KSHV malignancy. In this study, we show that KSHV replication and transcriptional activator (K‐RTA), an essential activator of the viral lytic cycle, transactivates the CD274/PD‐L1 gene promoter. Mechanistically, we demonstrate that the binding of K‐RTA to the cellular specificity protein 1 (SP1) is critical for K‐RTA–mediated CD274/PD‐L1 promoter activation. These findings suggest that K‐RTA cooperates with intracellular SP1 to activate the expression of CD274/PD‐L1, which helps the virus regulate immune checkpoints to escape and survive.