PAD4 regulates proliferation of hematopoietic multipotent progenitors by directly controlling c-Myc expression. (111.7)

Abstract

Abstract Peptidylarginine deiminase 4 (PAD4) functions as a transcriptional co-reporessor by catalyzing the conversion of arginine to citrulline residues of histone H3. Although the high expression of PAD4 in the bone marrow may suggest its involvement in the hematopoiesis, its precise contribution remains unclear. Here we found that PAD4 is highly expressed in the hematopoietic stem and multipotent cells (Lineage-Sca1+c-kit+; termed LSK cells). Microarray and RT-qPCR analysis showed that the mRNA level of c-myc in PAD4-deficient (PADI4-/-) LSK cells was increased compared to PADI4+/+ LSK cells. Chromatin immunoprecipitation assay showed that in LSK cells, PAD4 targeted to the upstream of c-myc gene, suggesting that PAD4 might catalyze the citrullination and reduce the arginine methylation in histone H3. Furthermore, PAD4 was associated with the transcription factor LEF1 as well as histone deacetylase 1 (HDAC1). These results indicated that PAD4 suppressed c-Myc expression by histone citrullination acting as a suppressor complex with LEF1 and HDAC1 in LSK cells. Supporting these findings, PADI4-/- LSK cells showed an advanced proliferation in a cell-autonomous fashion, resulting in increase in number compared to PADI4+/+ LSK cells. Together, our results strongly suggest that PAD4 regulates the proliferation of LSK cells via controlling c-Myc expression, implying that PAD4 may be involved in pathogenesis of some myeloproliferative diseases.