title: Phosphorylation status of transcription factor C/EBPalpha determines cell-surface poly-LacNAc branching (I antigen) formation in erythropoiesis and granulopoiesis.
abstract: The cell-surface straight and branched repeats of N-acetyllactosamine (LacNAc) units, called poly-LacNAc chains, characterize the histo-blood group i and I antigens, respectively. The transition of straight to branched poly-LacNAc chain (i to I) is determined by the I locus, which expresses 3 IGnT transcripts, IGnTA, IGnTB, and IGnTC. Our previous investigation demonstrated that the i-to-I transition in erythroid differentiation is regulated by the transcription factor CCAAT/enhancer binding protein alpha (C/EBPalpha). In the present investigation, the K-562 cell line was used as a model to show that the i-to-I transition is determined by the phosphorylation status of the C/EBPalpha Ser-21 residue, with dephosphorylated C/EBPalpha Ser-21 stimulating the transcription of the IGnTC gene, consequently resulting in I branching. Results from studies using adult erythropoietic and granulopoietic progenitor cells agreed with those derived using the K-562 cell model, with lentiviral expression of C/EBPalpha in CD34(+) hematopoietic cells demonstrating that the dephosphorylated form of C/EBPalpha Ser-21 induced the expression of I antigen, granulocytic CD15, and also erythroid CD71 antigens. Taken together, these results demonstrate that the regulation of poly-LacNAc branching (I antigen) formation in erythropoiesis and granulopoiesis share a common mechanism, with dephosphorylation of the Ser-21 residue on C/EBPalpha playing the critical role.
authors.affiliation: Institute of Biochemical Sciences, National Taiwan University, Taipei 106, Taiwan.
authors.forename: Yuh-Ching
authors.initials: YC
authors.lastname: Twu
authors.forename: Chuang-Yi
authors.initials: CY
authors.lastname: Hsieh
authors.forename: Marie
authors.initials: M
authors.lastname: Lin
authors.forename: Cheng-Hwai
authors.initials: CH
authors.lastname: Tzeng
authors.forename: Chien-Feng
authors.initials: CF
authors.lastname: Sun
authors.forename: Lung-Chih
authors.initials: LC
authors.lastname: Yu
mesh_terms: D018952:Antigens, CD34 / Q000378:metabolism; D022763:CCAAT-Enhancer-Binding Protein-alpha / Q000235:genetics / Q000378:metabolism*; D002240:Carbohydrate Sequence; D002454:Cell Differentiation / Q000502:physiology; D004920:Erythropoiesis / Q000502:physiology*; D006098:Granulocytes / Q000166:cytology / Q000378:metabolism*; D006801:Humans; D007048:I Blood-Group System / Q000378:metabolism*; D020014:K562 Cells; D008565:Membrane Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D017351:N-Acetylglucosaminyltransferases / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation / Q000502:physiology; D011134:Polysaccharides / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000502:physiology; D012694:Serine / Q000235:genetics
chemical_list: D018952:Antigens, CD34; D022763:CCAAT-Enhancer-Binding Protein-alpha; D007048:I Blood-Group System; D008565:Membrane Proteins; D011134:Polysaccharides; D012694:Serine; C037199:poly-N-acetyllactosamine; C106501:N-acetylglucosaminyltransferase IGnT; D017351:N-Acetylglucosaminyltransferases