Site specific target binding controls RNA cleavage efficiency by the Kaposi’s sarcoma-associated herpesvirus endonuclease SOX

Aaron S. Mendez; Carolin Vogt; Jens Bohne; Britt A. Glaunsinger

Viral infection dramatically reshapes the gene expression landscape of the host cell. By changing overall messenger RNA (mRNA) abundance or translation, viruses can redirect host machinery towards viral gene expression while simultaneously dampening immune stimulatory signals (1) (2) (3) . Suppression of host gene expression, termed host shutoff, can occur via a variety of mechanisms, but one common strategy is to accelerate degradation of mRNA (1, 2) . This occurs during infection with DNA viruses such as In cells, the mRNA fragments resulting from the primary SOX endonucleolytic cleavage are predominantly cleared by the host 5'-3' exonuclease XRN1, while in vitro, RNA fragments are rapidly degraded by 5'-3' exonucleolytic activity intrinsic to purified SOX (9) . Thus, it has been challenging to analyze the initial endonucleolytic cleavage event that is an essential component of mRNA target specificity in vivo. Here, we sought to develop a biochemical system to address these questions.