IDENTIFICATION OF HOMOMERIC AND HETEROMERIC INTERACTIONS BETWEEN MEMBERS OF THE BREAST CARCINOMA-ASSOCIATED D52 PROTEIN FAMILY USING THE YEAST 2-HYBRID SYSTEM

The hD52 gene was originally identified through its elevated expressio n level in human breast carcinoma. Cloning of D52 homologues from othe r species has indicated that D52 may play roles in calcium-mediated si gnal transduction and cell proliferation. Two human homologues of hD52 , hD53 and hD54, have also been identified, demonstrating the existenc e of a novel gene/protein family. Since D52-like protein sequences are all predicted to contain a coiled-coil domain, we used the yeast two- hybrid system and glutathione S-transferase pull-down assays to invest igate whether homo- and/or heteromeric interactions occur between D52- like proteins. Analyses of yeast strains co-transfected with paired D5 2-like constructs indicated that D52-like fusion proteins interact in homo- and heteromeric fashions through their predicted coiled-coil dom ains. Similarly, extensive two-hybrid screenings of a human breast car cinoma expression library identified hD53 and hD52 as potential intera ctors for both hD52 and hD53 baits. Thus, D52-like proteins appear to exert and/or regulate their activities through specific interactions w ith other D52-like proteins, which in turn may be intrinsic to potenti al roles of these molecules in controlling cell proliferation.