Characterization of a cDNA clone encoding murine mitogen-regulated protein: regulation of mRNA levels in mortal and immortal cell lines.

Mitogen-regulated protein (MRP) is secreted by certain immortal murine cell lines (Swiss 3T3, BNL) stimulated with serum or particular growth factors. We have identified a cDNA clone that encodes part of the protein and have confirmed that MRP is closely related to, if not identical to, the prolactin-related protein designated proliferin. MRP is not produced by primary mouse embryo fibroblasts to nearly the same extent as it is produced by many immortal or transformed lines. Control of expression of this protein by growth factors is achieved both by regulating the extent of transcription and by regulating the processing of the protein.