A translocated erythropoietin receptor gene in a human erythroleukemia cell
line (TF-1) expresses an abnormal transcript and a truncated protein
JC Winkelmann, J Ward, P Mayeux, C Lacombe, L Schimmenti and RB Jenkins
Department of Internal Medicine, University of Cincinnati College of
Medicine, OH.
We previously identified a translocation breakpoint in exon 8 of the
erythropoietin receptor (EpoR) gene in TF-1 cells, a cell line derived from
a human erythroleukemia. To investigate the potential pathogenetic
significance of this abnormality, we more precisely mapped the breakpoint
within exon 8 and studied the expression of the translocated gene by S1
nuclease mapping of EpoR transcripts and chemical crosslinking of labeled
erythropoietin (Epo) to TF-1 cell surface receptors. Transcripts from the
abnormal gene were found to be highly expressed in relation to normal EpoR
transcripts in TF-1 cells. The breakpoint predicted by S1 mapping of
abnormal EpoR transcripts agreed closely with that determined by Southern
analysis. Chemical cross- linking of 125I-Epo to TF-1 cells showed an
abnormal, low-molecular- weight cross-linked species directly recognized by
anti-EpoR antibodies and present in considerable excess over the normal
EpoR. Karyotype analysis showed that each of 10 TF-1 cell metaphases had,
in addition to multiple other alterations, one chromosome 19 with
additional chromosomal material translocated onto the short arm at 19p13.3,
the location of the EpoR gene. We conclude that the structurally abnormal
EpoR gene in TF-1 cells is highly expressed and produces an abnormal
protein. We speculate that the chromosomal material brought into the EpoR
locus by translocation is responsible for the high level of expression. We
hypothesize that this translocation participated in the evolution of the
erythroleukemia from which TF-1 cells were derived.
Volume 85,
Issue 1,
pp. 179-185,
01/01/1995
Copyright © 1995 by The American Society of Hematology
