Subcellular localization of the major immediate early protein (IE1) of human cytomegalovirus at early times after infection.

The immediate early (IE) 1 protein of human cytomegalovirus was investigated by subcellular fractionation and immunocolloidal gold electron microscopy. The IE1 protein is phosphorylated and detected on intracytoplasmic membranes at early times after infection. An electron microscopy study confirmed that the IE1 antigen was an intracytoplasmic membrane-associated protein at early times after infection. The IE1 antigen as well as the IE2 antigen was also detected in the nucleus. However, the IE1 antigen was not detected on the plasma membrane surface of infected cells. The role of this viral protein in the immune response is discussed.