EGR (early growth response) genes represent a family of the proteins whose structure includes a zinc finger domain(s) interacting with the specific site in regulatory sequences of different genes. Using as an antigen the short sequence RSNHLTTHIR from the middle of the zinc finger domain of EGR-1 we have generated a clone of the hybridoma cells producing the monoclonal antibody (mAb) that binds to 102 kD and 58 kD proteins, but apparently does not bind EGR-1 protein. The 102 kD protein is probably made of the 58 kD subunit and another one of 44 kD. Expression of these proteins is strongly induced in serum stimulated mouse fibroblasts.