Kaposi's Sarcoma-Associated Herpesvirus Utilizes and Manipulates RNA N 6 -Adenosine Methylation To Promote Lytic Replication.

N6 -adenosine methylation (m6 A) is the most common posttranscriptional RNA modification in mammalian cells. We found that most transcripts encoded by the Kaposi's sarcoma-associated herpesvirus (KSHV) genome undergo m6 A modification. The levels of m6 A-modified mRNAs increased substantially upon stimulation for lytic replication. The blockage of m6 A inhibited splicing of the pre-mRNA encoding the replication transcription activator (RTA), a key KSHV lytic switch protein, and halted viral lytic replication. We identified several m6 A sites in RTA pre-mRNA crucial for splicing through interactions with YTH domain containing 1 (YTHDC1), an m6 A nuclear reader protein, in conjunction with serine/arginine-rich splicing factor 3 (SRSF3) and SRSF10. Interestingly, RTA induced m6 A and enhanced its own pre-mRNA splicing. Our results not only demonstrate an essential role of m6 A in regulating RTA pre-mRNA splicing but also suggest that KSHV has evolved a mechanism to manipulate the host m6 A machinery to its advantage in promoting lytic replication. IMPORTANCE KSHV productive lytic replication plays a pivotal role in the initiation and progression of Kaposi's sarcoma tumors. Previous studies suggested that the KSHV switch from latency to lytic replication is primarily controlled at the chromatin level through histone and DNA modifications. The present work reports for the first time that KSHV genome-encoded mRNAs undergo m6 A modification, which represents a new mechanism at the posttranscriptional level in the control of viral replication.