The identification of ferritin in the nucleus of K562 cells, and investigation of a possible role in the transcriptional regulation of adult beta-globin gene expression.
We studied the subcellular distribution of ferritin in K562 cells by immunofluorescence techniques and have made a reappraisal of a direct binding interaction between ferritin and the proximal promoter region of the human beta-globin gene, as previously mentioned in the literature. Confocal microscopy indicates that ferritin, the iron-storage protein, is present in the nucleus of K562 cells, in addition to its expected cytoplasmic localisation. The stain distribution suggests that it is not directly associated with the nuclear matrix. Using a gel mobility shift assay, a protein that cross-reacts with monoclonal ferritin antibodies competitively binds to a double-stranded oligonucleotide spanning the region situated 150 base pairs upstream from the beta-globin transcription start site. Despite this antibody cross-reactivity, the protein is unlike cytosolic ferritin as it appears to be highly sensitive to both temperature and freeze-thaw cycles, and UV-crosslinking experiments indicate that the molecular mass of the protein factor lies between 90 and 100 kDa. In conclusion, while the intranuclear location of ferritin is described in the present study, ferritin is not in direct contact with the beta-globin promoter region.
Pountney
D
D
INSERM Unité 409, Faculté de Medecine Xavier Bichat, 75018 Paris, France.
Trugnan
G
G
Bourgeois
M
M
Beaumont
C
C
D000328:Adult; D000818:Animals; D001483:Base Sequence; D002467:Cell Nucleus / Q000378:metabolism / Q000648:ultrastructure*; D003593:Cytoplasm / Q000648:ultrastructure; D005293:Ferritins / Q000032:analysis* / Q000378:metabolism*; D005786:Gene Expression Regulation; D005914:Globins / Q000235:genetics*; D006801:Humans; D020014:K562 Cells / Q000648:ultrastructure*; D018613:Microscopy, Confocal; D011401:Promoter Regions, Genetic; D016415:Sequence Alignment; D012689:Sequence Homology, Nucleic Acid; D014158:Transcription, Genetic; D014162:Transfection
D005914:Globins; D005293:Ferritins