Transcriptional regulation of the KEL gene and Kell protein expression in erythroid and non-erythroid cells.
The Kell blood-group antigen was originally reported to be a protein expressed in erythroid tissue only. Transcriptional analysis of the KEL promoter activity in human erythroleukaemia K562 and epithelial HeLa cells by electrophoretic mobility-shift and supershift assays, chloramphenicol acetyltransferase assays, co-transfection studies and site-directed mutagenesis provided the following results: (i) the KEL promoter exhibits a strong transcriptional activity in K562 cells and, unexpectedly, a basal non-erythroid activity in HeLa cells, (ii) up-regulation of the 5' distal promoter activity occurs only in the erythroid context, and (iii) two motifs localized in the exon 1 region, which bind the Sp1/Sp3 and the human GATA-1/Ku70/80 factors, were required for down-regulation of the promoter activity, but inhibition of the promoter activity by the repressing factors in HeLa cells was incomplete. KEL expression in HeLa cells was performed further by primer-extension analysis, which revealed the presence of a low amount of Kell transcript correlating with basal expression of the Kell protein in these cells, as shown by immunopurification and Western-blot analysis. DNA sequencing of the transcript revealed a sequence identical to that obtained from erythroid tissue. In human tissues, KEL expression was investigated by dot-blot analysis and revealed high levels of Kell mRNAs, particularly in brain tissues, testis and lymphoid tissues. Moreover, most tissues analysed exhibited low levels of Kell transcripts. The Kell protein was also detected by immunohistochemistry in the Sertoli cells of the testis and in lymphoid tissues like spleen and tonsil, specifically localized in the follicular dendritic cells. Altogether, the results indicated that KEL expression is not restricted to erythroid tissue.
Camara-Clayette
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INSERM U76, Institut National de la Transfusion Sanguine, 6, rue Alexandre Cabanel, 75015 Paris, France.
Rahuel
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Lopez
C
C
Hattab
C
C
Verkarre
V
V
Bertrand
O
O
Cartron
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JP
D034961:Antigens, Nuclear; D015500:Chloramphenicol O-Acetyltransferase; D004265:DNA Helicases; D004268:DNA-Binding Proteins; D015672:Erythroid Precursor Cells; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D006367:HeLa Cells; D006801:Humans; D020014:K562 Cells; D007626:Kell Blood-Group System / Q000235:genetics*; D000072200:Ku Autoantigen; D008156:Luciferases; D008221:Lymphoid Tissue; D008297:Male; D009687:Nuclear Proteins; D017354:Point Mutation; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D013737:Testis; D014018:Tissue Distribution; D014157:Transcription Factors / Q000378:metabolism
D034961:Antigens, Nuclear; D004268:DNA-Binding Proteins; D007626:Kell Blood-Group System; D009687:Nuclear Proteins; D014157:Transcription Factors; D008156:Luciferases; D015500:Chloramphenicol O-Acetyltransferase; D004265:DNA Helicases; C106893:XRCC5 protein, human; C000606509:Xrcc6 protein, human; D000072200:Ku Autoantigen