The herpes simplex virus type 1 (HSV-1) infected-cell protein 27 (ICP27) is an essential, highly conserved protein involved in various steps of HSV-1 gene regulation as well as in the shut-off of host gene expression during infection. It functions primarily at the post-transcriptional level in inhibiting precursor mRNA splicing and in promoting nuclear export of viral transcripts. Recently, many novel functions performed by the HSV-1 ICP27 protein were shown, including leptomycin B resistance, inhibition of the typeⅠinterferon signaling, regulation of the viral mRNA translation and determining the composition of HSV-1 virions.