The proapoptotic factor Nix is coexpressed with Bcl-xL during terminal erythroid differentiation.
Transcriptional profiles of cultured primary human erythroid cells were examined to identify those genes involved in the control of erythroid growth during the terminal phase of maturation. Our in silico screening strategy indicated that a hypoxia-inducible proapoptotic member of the Bcl-2 gene family called Nix is expressed during erythropoiesis. We next performed Northern blot analyses and determined that the 1.4-kb Nix transcript is expressed at lower levels in erythroleukemia cells than reticulocytes. Polymerase chain reaction (PCR)-based transcriptional patterning confirmed the increased expression of Nix during human erythropoiesis with a pattern similar to that of Bcl-xL and glycophorin A and opposite that of Bcl-2. Western blot analyses revealed Nix protein levels that were lower than expected due to increased proteosomal degradation. The expression of Nix and Bcl-xL proteins decreased relative to glyceraldehyde-3-phosphate dehydrogenase (GAPDH) control on the removal of erythropoietin (EPO) from the culture medium. Immunocytochemical analyses demonstrated a similar perinuclear mitochondrial expression pattern for both proteins in hemoglobinized precursors. On the basis of these data, we propose that the proapoptotic factor Nix is a highly regulated effector of growth during terminal erythroid maturation.
Aerbajinai
Wulin
W
Laboratory of Chemical Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, USA.
Giattina
Mara
M
Lee
Y Terry
YT
Raffeld
Mark
M
Miller
Jeffery L
JL
D017209:Apoptosis / Q000235:genetics; D015153:Blotting, Western; D002454:Cell Differentiation / Q000187:drug effects / Q000235:genetics; D003546:Cysteine Endopeptidases / Q000378:metabolism; D015672:Erythroid Precursor Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D004920:Erythropoiesis / Q000235:genetics*; D004921:Erythropoietin / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects; D006021:Glycophorins / Q000096:biosynthesis / Q000235:genetics; D006801:Humans; D004915:Leukemia, Erythroblastic, Acute / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D008565:Membrane Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000502:physiology; D009097:Multienzyme Complexes / Q000378:metabolism; D016133:Polymerase Chain Reaction; D046988:Proteasome Endopeptidase Complex; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis* / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D012156:Reticulocytes / Q000187:drug effects / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects; D014407:Tumor Cells, Cultured / Q000378:metabolism; D025521:Tumor Suppressor Proteins; D051020:bcl-X Protein
C494811:BCL2L1 protein, human; C116838:BNIP3L protein, human; D006021:Glycophorins; D008565:Membrane Proteins; D009097:Multienzyme Complexes; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D025521:Tumor Suppressor Proteins; D051020:bcl-X Protein; D004921:Erythropoietin; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex