C/EBPε ΔRS derived from a neutrophil-specific granule deficiency patient interacts with HDAC1 and its dysfunction is...

CCAAT/enhancer binding protein epsilon (C/EBPε), a myeloid-specific transcription factor, plays an important role in granulopoiesis. A loss-of-function mutation in this protein can result in an abnormal development of neutrophils and eosinophils, known as neutrophil-specific granule deficiency (SGD). The transcriptional activity of C/EBPε is regulated by interactions with other transcription factors and/or post-translational modification, including acetylation. Previously, we reported a novel SGD patient who had a homozygous mutation for two amino acids, arginine (R247) and serine (S248), which were deleted in the basic leucine zipper domain of C/EBPε (ΔRS) and exhibited loss of transcriptional activity with aberrant protein-protein interactions. In the present study, we found that a single amino acid deletion of either R247 (ΔR) or S248 (ΔS) was sufficient for the loss of C/EBPε transcriptional activity, while an amino acid substitution at S248 to alanine in C/EBPε (SA) had comparable transcriptional activity with the wild-type C/EBPε (WT). Although acetylation at lysine residues (K121 and K198) is indispensable for C/EBPε transcriptional activity, an acetylation mimic form of ΔRS (ΔRS-K121/198Q) did not exhibit the transcriptional activity. Interestingly, we discovered that ΔRS, ΔR, ΔS, and ΔRS-K121/198Q interacted with histone deacetylase 1 (HDAC1), whereas WT and SA did not. Furthermore, the proteoglycan 2/eosinophil major basic protein induction activity of ΔRS, ΔR, and ΔS could be restored by the HDAC inhibitor, trichostatin A (TSA), and protein-protein interactions between ΔRS and Gata1 could also be recovered by TSA treatment. Taken together, our results show that TSA has the potential to restore the transcriptional activity of ΔRS, indicating that the inhibition of HDAC1 could be a molecularly targeted treatment for SGD with ΔRS.