IDENTIFICATION OF GENE-SEQUENCES OVEREXPRESSED IN SENESCENT AND WERNER SYNDROME HUMAN FIBROBLASTS

The phenotype of replicative senescence is a dominant trait in human d iploid fibroblasts (HDF), Therefore, we have sought to identify overex pressed and/or newly expressed causal genes by constructing and screen ing a subtracted cDNA library derived from polyA(+)RNA of prematurely senescent Werner syndrome (WS) HDF, We have identified 15 cDNA clones that are overexpressed in senescent and WS HDF, Among them are six kno wn sequences coding for: acid sphingomyelinase, fibronectin, SPARC, nm 23-metastasis suppressor protein, and two translation factors, eIF-2 b eta and EF-1 alpha. Among the 10 unknown clones are: S1-5, which encod es a secreted protein containing EGF-like domains and paradoxically st imulates DNA synthesis of young HDF in an autocrine and paracrine mann er; S1-3, which encodes a protein containing ''zinc finger'' domains, suggesting nucleic acid binding properties; S1-15, which shows sequenc e similarities to human alpha 2-chimerin; and S2-6, which represents a new member of the LIM family of proteins. The other five clones do no t have any significant homology to known sequences. Steady-state mRNA levels of all gene sequences thus far studied are elevated in both WS and senescent normal HDF when compared to young HDF,which suggests tha t senescent and WS HDF enter a final common pathway where multiple gen e overexpression may generate diverse antiproliferative mechanisms and pathogenic sequelae.