The characteristic which makes the cell-coded HSV-inducible U90 distinctive in transformed cells is its greatly increased half-life.

A set of polypeptides detected in transformed cells of M(r) values 90,000 (a doublet) 40,000 and 32,000 that are recognised by immunoprecipitation of L-[35S]methionine-labelled tumour cell lysates, with sera from tumour-bearing rats and with antisera raised against herpes simplex virus type 2 (HSV-2)-infected cells, were previously reported (Macnab et al., 1985, 1992; Hewitt et al., 1991). These proteins are cell-coded and cannot be precipitated from similarly radiolabelled control cells. Two of these polypeptides are significantly induced by HSV-2 infection (Hewitt et al., 1991; Macnab et al., 1992). This paper further characterises one of these polypeptides, U90, and addresses which properties distinguish the behaviour of U90 in tumour cells, whether there is an equivalent in control cells and whether U90 can be induced without HSV replication. U90 can be immunoprecipitated from radiolabelled human cells which are capable of extended passage in culture, as well as from human tumour cells, rodent tumour cells and cells of different lineages, e.g. epithelial, fibroblastic and lymphoid. Purification of U90 and the subsequent production of monospecific antibodies revealed, by western blotting, a homologue of 90 kDa in control cells. Western blotting shows that HSV can increase the amount of the U90 homologue in these normal cells. The absence of an immunoprecipitate of the U90 homologue from control cells is a result of the very short half-life (i.e. high turnover) of the protein in these cells (32.9 minutes) as opposed to tumour cells (about 13 hours).(ABSTRACT TRUNCATED AT 250 WORDS)