During herpes simplex virus type 1 (HSV-1) infection, the viral UL31 protein interacts with and forms a complex with the UL34 protein at the cellular inner nuclear membranes, where both play important roles in the envelopment and egress of nucleocapsids into cytoplasm.To characterise the mechanism of HSV-1 nucleocapsid egress by UL31 and UL34, we screened host proteins that are capable of interacting with UL31 in cells via yeast two-hybridisation, and transmembrane protein 140 (TMEM140), which has an unknown function, was identified and confirmed as binding to and colocalising with UL31 in the nucleus upon transfection with UL31 or viral infection.