Proteomic discovery of Max as a novel interacting partner of C/EBP alpha: a Myc/Max/Mad link

作者：Zada A A; Pulikkan J A; Bararia D; Geletu M; Trivedi A K; Balkhi M Y; D Hiddemann W; Tenen D G; Behre H M; Behre G^*

来源：Leukemia, 2006, 20(12): 2137-2146.

DOI：10.1038/sj.leu.2404438

• C/EBP alpha
• proteomics
• Myc-Max-Mad network
• mass spectrometry
• differentiation

The transcription factor CCAAT/enhancer binding protein a (C/EBP alpha) is important in the regulation of granulopoiesis and is disrupted in human acute myeloid leukemia. In the present study, we sought to identify novel C/EBP alpha interacting proteins in vivo through immunoprecipitation using mass spectrometry-based proteomic techniques. We identified Max, a heterodimeric partner of Myc, as one of the interacting proteins of C/EBP alpha in our screen. We confirmed the in vivo interaction of C/EBP alpha with Max and showed that this interaction involves the basic region of C/EBP alpha. Endogenous C/EBP alpha and Max, but not Myc and Max, colocalize in intranuclear structures during granulocytic differentiation of myeloid U937 cells. Max enhanced the transactivation capacity of C/EBP alpha on a minimal promoter. A chromatin immunoprecipitation assay revealed occupancy of the human C/EBP alpha promoter in vivo by Max and Myc under cellular settings and by C/EBP alpha and Max under retinoic acid induced granulocytic differentiation. Interestingly, enforced expression of Max and C/EBP alpha results in granulocytic differentiation of the human hematopoietic CD34+ cells, as evidenced by CD11b, CD15 and granulocyte colony-stimulating factor receptor expression. Silencing of Max by short hairpin RNA in CD34+ and U937 cells strongly reduced the differentiation-inducing potential of C/EBP alpha, indicating the importance of C/EBP alpha-Max in myeloid progenitor differentiation. Taken together, our data reveal Max as a novel co-activator of C/EBPa functions, thereby suggesting a possible link between C/EBPa and Myc-Max-Mad network.

• 出版日期2006-12
• 单位河北医科大学