Abstract
Many tumor viruses encode oncogenes of cellular origin. Here, we report an oncoviral mimic of a cellular tumor suppressor. The Kaposi's sarcoma-associated herpesvirus (KSHV) microRNA (miRNA) miR-K6-5p shares sequence similarity to the tumor-suppressive cellular miR-15/16 miRNA family. We show that miR-K6-5p inhibits cell cycle progression, a hallmark function of miR-16. miR-K6-5p regulates conserved miR-15/16 family miRNA targets, including many cell cycle regulators. Inhibition of miR-K6-5p in KSHV-transformed B cells confers a significant growth advantage. Altogether, our data show that KSHV encodes a functional mimic of miR-15/16 family miRNAs. While it is exceedingly well established that oncogenic viruses encode oncogenes of cellular origin, this is an unusual example of an oncogenic virus that encodes a viral mimic of a cellular tumor suppressor. Encoding a tumor-suppressive miRNA could help KSHV balance viral oncogene expression and thereby avoid severe pathogenesis in the healthy host.