Identification, nuclear localization, and binding activities of OZF: A human protein solely composed of zinc-finger motifs

The OZF cDNA was identified in a human mammary cell line and encodes a polypeptide solely composed of ten zinc-finger motifs which belongs to the Kruppel family of zinc-finger proteins. The OZF protein produced in Escherichia coli binds zinc ions, DNA and heparin. These binding activities are characteristic of zinc-finger proteins. Immunochemical analysis using antibodies produced against the recombinant protein detected its expression in human mammary epithelial cells but not in stroma cells, which is consistent with the pattern of expression observed at the RNA level in cell cultures. Western blot analysis demonstrated the expression of a 33-kDa nuclear protein similar in size to the predicted protein and therefore excluded the presence of an additional trans-acting domain. These data establish the unique structure of the OZF protein which is distinct from previously identified zinc-finger proteins. In addition, OZF protein overexpression was found in a tumor cell line, which suggests a possible involvement in carcinogenesis.