MADM, a Novel Adaptor Protein That Mediates Phosphorylation of the 14-3-3 Binding Site of Myeloid Leukemia Factor 1

• Published in: The Journal of biological chemistry 2002-10, Vol.277 (43), p.40997-41008
• Main Authors: Lim, Raelene, Winteringham, Louise N, Williams, James H, McCulloch, Ross K, Ingley, Evan, Tiao, Jim Y-H, Lalonde, Jean-Philippe, Tsai, Schickwann, Tilbrook, Peta A, Sun, Yi, Wu, Xiaohua, Morris, Stephan W, Klinken, S Peter
• Format: Article
• Language: English
• Subjects: 14-3-3 Proteins; Adaptor Proteins, Vesicular Transport - chemistry; Adaptor Proteins, Vesicular Transport - genetics; Adaptor Proteins, Vesicular Transport - metabolism; Amino Acid Sequence; Animals; Base Sequence; Binding Sites; Cell Cycle Proteins; COS Cells; Dimerization; DNA, Complementary; DNA-Binding Proteins; Humans; Molecular Sequence Data; Phosphorylation; Precipitin Tests; Proteins - chemistry; Proteins - metabolism; Receptors, Cytoplasmic and Nuclear; Sequence Homology, Amino Acid; Tyrosine 3-Monooxygenase - chemistry; Tyrosine 3-Monooxygenase - metabolism; Vesicular Transport Proteins
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M206041200

A yeast two-hybrid screen was conducted to identify binding partners of Mlf1, an oncoprotein recently identified in a translocation with nucleophosmin that causes acute myeloid leukemia. Two proteins isolated in this screen were 14-3-3ζ and a novel adaptor, Madm. Mlf1 contains a classic RS X S X P sequence for 14-3-3 binding and is associated with 14-3-3ζ via this phosphorylated motif. Madm co-immunoprecipitated with Mlf1 and co-localized in the cytoplasm. In addition, Madm recruited a serine kinase, which phosphorylated both Madm and Mlf1 including the RS X S X P motif. In contrast to wild-type Mlf1, the oncogenic fusion protein nucleophosmin (NPM)-MLF1 did not bind 14-3-3ζ, had altered Madm binding, and localized exclusively in the nucleus. Ectopic expression of Madm in M1 myeloid cells suppressed cytokine-induced differentiation unlike Mlf1, which promotes maturation. Because the Mlf1 binding region of Madm and its own dimerization domain overlapped, the levels of Madm and Mlf1 may affect complex formation and regulate differentiation. In summary, this study has identified two partner proteins of Mlf1 that may influence its subcellular localization and biological function.