EXPRESSION OF THE NEUROFIBROMATOSIS-1 (NF1) GENE DURING GROWTH ARREST

THE neurofibromatosis 1 (NF1) gene product, neurofibromin, is a tumor suppressor gene product capable of inhibiting the growth of cells in c ulture. If neurofibromin suppresses cell growth by arresting cells in G(0) or G(1), its expression might be regulated in a cell cycle-depend ent fashion. In this study, we demonstrate that RAT-1A fibroblasts arr ested in G(0)/G(1) by serum starvation and then released to progress t hrough the cell cycle do not demonstrate significant changes in NF1 ex pression. However, when arrested in G(0)/G(1) by contact inhibition, N F1 expression in these cells is reversibly upregulated within 72 h, su ggesting that NF1 expression is a late event associated with cell grow th arrest which may contribute to the maintenance of the differentiate d state.