Abstract
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 the 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 effects on cell growth studied. Addition of U90 to quiescent fibroblast cells stimulated the 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.