The cell-coded polypeptide U90 increased by herpes simplex virus type 2 infection induces Fos and DNA synthesis

Lytic infection with herpes simplex virus type 2 (HSV-2) induces synthesis of a cell-coded protein of molecular mass 90 kDa, termed U90. U90, whose expression is specific in tumour cells is, in addition, excreted from he cell. To determine if the function of U90 could be advantageous for the virus the protein was purified from the medium of HSV-2 infected cells, shown to be similar to the internalized form and its effect on cell growth studied. Addition of U90 to quiescent fibroblast cells stimulated teh expression of Fos, the product of the cellular transcription factor c-fos and increased the incorporation of [3H]thymidine into DNA, factors which may facilitate HSV-2 replication. However, U90 might also induce abnormal cells such as those in precancerous lesions to proliferate.