Suppression of Ras-mediated NIH3T3 transformation by p19^ARF does not involve alterations of cell growth properties

Abstract

The INK4a gene, one of the most frequently disrupted loci in human cancer, encodes two unrelated proteins, p16^INK4a and p19^ARF, that both block cell proliferation. p16^INK4a is a component of the Rb regulatory pathway, while p19^ARF has been functionally related to p53. Moreover, p16^INK4a is inactivated in many human tumors, while it has been very recently reported that p19^ARF null mice develop tumors early in life. We show here that p19^ARF is able to inhibit the formation of G418-resistant colonies when transfected into human and mouse cell lines expressing wild-type p53, regardless of p16 status. Moreover its amino terminal domain encoded by exon 1β is still sufficient to obtain the same effect. We have analysed the ability of p19^ARF to interfere with Ras-mediated cellular transformation in the NIH3T3 cell line. Cotransfection of p19^ARF together with activated ras potently inhibited the formation of transformed foci in a dose-dependent manner. We have also isolated stable NIH3T3 transfectants expressing p19^ARF and we have measured their growth properties as well as their efficiency of transformation by activated ras. Our results suggest that p19^ARF can interfere with oncogene-mediated transformation, without significantly affecting NIH3T3 cell growth, at least at the levels of expression achieved in these experiments.