Functional interaction of transcriptional coactivator ASC-2 and C/EBPα in granulocyte differentiation of HL-60 promyelocytic cell

HL-60 promyelocytic eels were treated with retinoic acid (RA) to stimulate granulocyte differentiation. CCAAT/enhancer binding protein alpha (C/EBP alpha) is known to be the molecular switch during early hematopoietic developmental events that direct cells to the granulocytic pathway. Here we show that the coactivator activating signal cointegrator-2 (ASC-2) plays an important role in differentiation of HL-60 cells into granulocytes by mediating C/EBP alpha -induced gene transcription. The differentiation inducer RA increased mRNA and protein expression of ASC-S. The protein-protein interaction of C/EBP alpha and ASC-2 was detected by coimmunoprecipitation during granulocyte differentiation. Subsequently, GST-pull-down assay revealed that the N-terminal transactivation domain of C/EBPa could interact with ASC-2. This functional interaction of ASC-2 with C/EBPa drove a synergistic enhancement of C/EBP alpha -dependent transactivation and overexpression of the N-terminal C/EBP alpha protein in HL-60 cells inhibited ASC-2 responsiveness for C/EBP alpha activity in granulocyte differentiation, indicating C/EBP alpha dependency of ASC-2 activity. Taken together, these results suggest that the differentiation-dependent expressed ASC-S protein physically and functionally interacts with G/EBP alpha and increases its transactivation activity, regulating specific gene transcription for granulocyte differentiation. (C) 2001 Academic Press.