ANALYSIS OF EPC-1 GROWTH STATE-DEPENDENT EXPRESSION, SPECIFICITY, ANDCONSERVATION OF RELATED SEQUENCES

The transcipt for EPC-1 (early population doubling level (PDL) cDNA-1) is induced under conditions of growth arrest due to density-dependent contact inhibition and/or serum deprivation in early-passage but not in senescent WI-38 fibroblasts. We have characterized the EPC-1 transc ript with respect to its cell-cycle regulation, tissue specificity, an d interspecies conservation of related genomic sequences. In low densi ty, quiescent (serum-deprived), early-passage fibroblasts that are sti mulated to proliferate with fresh serum, steady-state EPC-1 transcript levels are steadily reduced until they reach a basal level approximat ely 24 h after stimulation. However, when early-passage fibroblasts ar e made quiescent by both serum deprivation and density-dependent conta ct inhibition and then stimulated with serum, steady-state EPC-1 trans cript levels remain relatively constant throughout a 36 h period follo wing serum stimulation. Senescent WI-38 cells (> 95% life span complet ed) do not express EPC-1 under these conditions. We show that differen ces in the regulation of EPC-1 transcript levels in early-passage cell s are due to differences in growth state rather than changes in cell d ensity or contact. We also show that expression of the EPC-1 transcrip t is limited to specific cell types and that related genomic sequences are found in all mam malian species examined as well as in the chicke n. (C) 1995 Wiley-Liss, Inc.