INHIBITION OF CELL-PROLIFERATION BY THE INTERFERON-INDUCIBLE 204-GENE, A MEMBER OF THE IFI-200 CLUSTER

The role of the IFN-inducible p204 as growth regulator was investigate d by transfecting an expression vector constitutively expressing p204 into several cell lines, Like PRE and p107, p204 is a potent growth in hibitor in sensitive cells, as demonstrated by the cell focus assay, S ince stable transfectants of sensitive lines constitutively overexpres sing p204 could not be established in vitro, we inserted the 204 cDNA into a vector bearing an heavy-metal-inducible promoter, Here we show that proliferation of B6MEF fibroblasts lacking endogenous p204 is str ongly inhibited by transient p204 expression in the nucleus, p204 dela ys G(1) progression into the S-phase and cells accumulate with a DNA c ontent equivalent to cells arrested in late G(1). Moreover, the role o f p204 in the control of cell growth in vivo was investigated by gener ating transgenic mice in which the Ifi 204 gene was constitutively exp ressed in all tissues, To this end, expression vectors bearing the 204 cDNA under the control of the SV40 viral promoter were constructed, T he overexpression of the p204 transgene achieved by injecting fertiliz ed mouse eggs with these vectors was compatible with embryo developmen t up to the four-cell stage in an in vitro follow-up of 4.5 days, Howe ver, no viable animals with an intact copy of the transgene were obtai ned, suggesting that high and constitutive levels of p204 expression c an impair normal embryo development, These findings indicate that p204 plays a negative role in growth regulation and provide new informatio n about the molecular mechanisms exploited by IFNs to inhibit cell pro liferation.