title: Regulation and localization of TOB and IFR1 in differentiating red cells.
abstract: In differentiating red blood cells (RBCs) of the chick embryo, the synthesis of carbonic anhydrase (CAII) and pyrimidine 5'-nucleotidase (P5N-I) is triggered by the hypoxic mediators norepinephrine and adenosine via receptor-mediated cAMP formation. The process is accompanied by the induction of IFR1 and TOB which are putative regulators of transcription or translation in different cell types. The present investigation studied the erythroid TOB and IFR1 expression: mRNA and protein are up-regulated in post-mitotic RBCs from D11-19 treated with cAMP-elevating agonists. In contrast, immature RBCs of early embryos (D5-7) fail to synthesize a significant amount of IFR1/TOB. In D11 RBCs, TOB and IFR1 are cytosolic proteins with different half-lives (TOB<4h, IFR1>12h). Cytosolic fractionation characterized TOB as a free soluble protein while the abundant IFR1 (c(max) approximately 3microM) is completely associated with the ribosomal fraction. A putative function of both proteins as translational regulators is discussed.
authors.affiliation: Institut für Physiologie, Universität Regensburg, Universitätsstr. 31, 93053 Regensburg, Germany.
authors.forename: Simone K
authors.initials: SK
authors.lastname: Steiner
authors.forename: Rosemarie
authors.initials: R
authors.lastname: Baumann
authors.forename: Stefanie
authors.initials: S
authors.lastname: Dragon
mesh_terms: D000818:Animals; D002454:Cell Differentiation; D002642:Chick Embryo / Q000166:cytology* / Q000378:metabolism*; D002645:Chickens; D004912:Erythrocytes / Q000166:cytology* / Q000378:metabolism*; D017874:Immediate-Early Proteins / Q000378:metabolism*; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D013347:Subcellular Fractions / Q000378:metabolism; D025521:Tumor Suppressor Proteins / Q000378:metabolism*
chemical_list: D017874:Immediate-Early Proteins; D047908:Intracellular Signaling Peptides and Proteins; C098669:TOB1 protein, human; D025521:Tumor Suppressor Proteins