CXXC Finger Protein 1 Is Required for Normal Proliferation and Differentiation of The PLB-985 Myeloid Cell Line

CXXC finger protein 1 (CFP1) binds to unmethylated CpG motifs in DNA, is a component of the mammalian Set1 histone methyltransferase complex, and is essential for zebrafish hematopoiesis. Transfection of the human PLB-985 myeloid cell line with a short hairpin RNA directed against the transcript encoding CFP1 results in 80% fewer colonies compared to a vector control, suggesting that CFP1 is required for survival of PLB-985 cells. One clone, CFP1–AS1, exhibits a 70% decrease in CFP1 protein levels and a slower doubling time due to an increase in the proportion of cells in G₁ and G₂ and a decrease of cells in S phase. CFP1–AS1 cells exhibit a 40% reduction of DNA methyltransferase 1 protein but contain normal levels of global genomic cytosine methylation. The CFP1–AS1 clone suffers from a defect of granulocytic differentiation, as approximately half of the cells fail to obtain a terminally differentiated nuclear architecture and fail to generate a respiratory burst. Similar results were obtained upon induction of monocyte/macrophage differentiation. Extended passaging of CFP1–AS1 cells resulted in increased levels of the CFP1 protein, to approximately 85% of wild-type levels, and concomitant rescue of myeloid differentiation. These results demonstrate a role for CFP1 in mammalian hematopoietic development.