AN ENDOPLASMIC RETICULUM-RETAINED HERPES-SIMPLEX VIRUS GLYCOPROTEIN-HIS ABSENT FROM SECRETED VIRIONS - EVIDENCE FOR REENVELOPMENT DURING EGRESS

Although it is generally accepted that one of the first steps of herpe svirus egress is the acquisition of an envelope by nucleocapsids buddi ng into the inner nuclear membrane, later events in the pathway are no t well understood. We tested the hypothesis that the virus then underg oes de-envelopment, followed by reenvelopment at membranes outside the endoplasmic reticulum (ER), by constructing a recombinant virus in wh ich the expression of an essential glycoprotein, gH, is restricted to the inner nuclear membrane-ER by means of the ER retention motif, KKXX . This targeting signal conferred the predicted ER localization proper ties on gH in recombinant virus-infected cells, and gH and gL polypept ides failed to become processed to their mature forms, Cells infected with the recombinant virus released particles with 100-fold less infec tivity than those released by cells infected with the wild-type parent virus, yet the number of enveloped virus particles released into the medium was unaltered. These particles contained normal amounts of go a nd VP16 but did not contain detectable amounts of gH, and these data a re consistent with a model of virus exit,whereby naked nucleocapsids i n the cytoplasm acquire their final envelope from a subcellular compar tment other than the ER-inner nuclear membrane.