Expression of the growth arrest specific genes in rat embryonic fibroblasts undergoing senescence

Replicative senescence is an in vitro biological phenomenon that results the irreversible growth arrest of mammalian cells. In contrast, cellular quiescence is reversible upon the addition of mitogens or replating. Quiescence is associated with the expression of a particular gene family--the growth arrest specific (GAS) genes. I have determined whether gas genes expression also associates with senescence, as well as whether serum stimulation of senescent cells has the same inhibiting effect as in quiescent cells. Analysis of RNA of cultures of rat embryonic fibroblasts suggests that gas-1 and gas-6 gene expression is associated with the irreversible growth arrest of senescence. However, serum was found to have a different effect upon gas-1 and gas-6 expression in quiescent and senescent cells, because its stimulation of quiescent cells results in a dramatic decrease of their RNA levels, but it had no effect in senescent cells. Finally, analysis of the data is raising the possibility that the gas-1 and gas-6 genes expression may also be associated with conditions of cellular stress.