Zfp281 expression and physical interaction with GATA1 in erythroid cells. (A) qRT-PCR analysis showing Zfp148 and Zfp281 mRNA levels relative to Gapdh (glyceraldehyde-3-phosphate dehydrogenase) in C57BL/6 mouse tissues. (B) Heat map of Zfp148 and Zfp281 mRNA levels in flow cytometric sorted erythroid progenitor cells from ex vivo differentiated PBMC (GSE22552)³¹  (left) and CD34⁺ cord blood cells (GSE53983)³²  (right). (C) Heat map showing mean copy number of Zfp148 and Zfp281 protein per erythroid progenitor cell, determined by mass spectrometry–based absolute quantification approach (PXD004313, PXD004314, PXD004315, and PXD004316).³³  Following the expansion of cord blood CD34⁺ cells, CD36⁺ progenitors were flow sorted and differentiated ex vivo under erythroid conditions. Erythroid Prog1 and 2 equates to burst-forming unit-erythroid (BFU-E) and colony-forming unit-erythroid (CFU-E) cells, respectably.³³  (D) Western blot analysis of Zfp281 protein in major hematopoietic organs, spleen (Sp), bone marrow (BM), and thymus (Th) in mice. (E) Western blot showing Zfp281 protein levels during erythroid ex vivo differentiation of hCD34⁺ cells. (F) Western blot analysis following streptavidin affinity purification (SA-IP) from nuclear extracts of MEL cells stably expressing Bir A alone or Bir A and recombinant GATA1 containing an amino-terminal FLAG and BirA recognition motif (FB-GATA1). Two percent of the input material is shown. (G) Western blot analysis following SA-IP from nuclear extracts of K562 cells stably expressing Bir A alone or Bir A and recombinant FB-Zfp148. Two percent of the input material is shown. (H) Western blot analysis following SA-IP from nuclear extracts of K562 cells stably expressing Bir A or Bir A and recombinant FB-Zfp281. Two percent of the input material is shown. Lg, large; Sm, small.