CLONING AND IDENTIFICATION OF GENES THAT ASSOCIATE WITH MAMMALIAN REPLICATIVE SENESCENCE

Cellular senescence and limited proliferative capacity of normal diplo id cells has a dominant phenotype over immortality of cancerous cells, suggesting its regulation by the expression of a set of genes. In ord er to isolate the genes that associate with senescence, we have employ ed a clonal system of conditional SV40 T antigen rat embryo fibroblast cell lines which undergo senescence upon T antigen inactivation, Cons truction of cDNA libraries from two conditional cell lines and applica tion of differential screening and subtractive hybridization technique s have resulted in the cloning of eight senescence-induced genes (SGP- 2/Apo J, alpha 1-procollagen, osteonectin, fibronectin, SM22, cytochro me C oxidase, GTP-alpha, and a novel gene) and a senescence-repressed gene (FRS-2). Three of these genes encode for extracellular matrix pro teins, others are involved in the calcium-dependent signal transductio n pathways, while the SGP-2/Apo J gene may have a cellular protective function. RNA analysis has shown that the senescence-associated genes are overexpressed in both normal rat embryonic fibroblasts and human o steoblasts cell cultures undergoing aging in vitro. In comparison, the expression of these genes in a rat fibroblast immortalized cell line (208F cells) was down-regulated after both its partial and its full tr ansformation by ras oncogenes. Thus, cloning of senescence-associated genes opens up new ways to elucidate and/or to modulate aging and canc er. (C) 1998 Academic Press.