Herpes simplex virus type 1 abrogates the antiviral activity of Ch25h via its virion host shutoff protein.

Cholesterol 25-hydroxylase (Ch25h) is an interferon-inducible protein, and recent studies have demonstrated that it inhibited the replication of many enveloped viruses. However, in this study, we found that cells infected with wild-type (WT) HSV-1 reduced the expression of Ch25h, and ectopic expression of Ch25h could not inhibit the replication of WT-HSV-1. By screening assay, HSV-1 UL41 protein was found to down-regulate the expression of Ch25h. In addition, UL41 abrogated the antiviral activity of Ch25h via degrading its mRNA. Furthermore, ectopic expression of Ch25h inhibited the replication of UL41-null mutant HSV-1 (R2621), but not WT-HSV-1, and knockdown of Ch25h did not affect the replication of WT-HSV-1, but promoted the replication of the R2621. For the first time, HSV-1 UL41 was demonstrated to evade the antiviral function of Ch25h via its endonuclease activity.