The US11 gene product of herpes simplex virus has intercellular trafficking activity

The US11 gene product of herpes simplex virus is an abundant virion structu ral protein with RNA-binding regulatory activity. Its carboxyl-terminal hal f consists of tandem tripeptide repeats of the sequence RXP. We demonstrate that the US11 protein has intercellular trafficking activity and accumulat es in the nucleolus when singly expressed in cultured cells, and that the R XP repeats are responsible for this activity. These same properties were al so observed in cells expressing a fusion protein linking US11 to the green fluorescent protein. Furthermore, exogenous US11 protein was internalized b y cells at 4 degreesC, which suggests that US11 protein uptake occurs prima rily through an energy-independent pathway. (C) 2001 Academic Press.