Herpes simplex virus ICP27 increases translation of a subset of viral late mRNAs.

The herpes simplex virus (HSV) ICP27 immediate-early protein plays an essential role in the expression of viral late genes. ICP27 is a multifunctional protein and has been reported to regulate multiple steps of mRNA synthesis and processing, including transcription, splicing, and nuclear export. Recently, ICP27 was reported to interact with translation factors and to stimulate translation of the viral late mRNA encoding VP16. We examined the effects of ICP27 on accumulation, nuclear export, and translation of HSV 1 (HSV-1) late mRNAs encoding VP16, ICP5, and gD. We confirm here that ICP27 stimulates translation of VP16 mRNA as well as an additional HSV-1 late ICP5 mRNA. The data presented here demonstrate that translation levels of both VP16 and ICP5 mRNA is reduced during infections with the ICP27-null virus mutant d27-1, and with ICP27 C-terminal deletion mutant viruses n406 and n504, compared to wild-type virus. In contrast, the translation of gD mRNA is not affected by the presence of ICP27 during infection. These data demonstrate that ICP27 functions to increase the translation levels of a subset of HSV-1 late genes, and this function requires the C terminus of ICP27.