Embryonal Carcinoma P19 Cells Produce Erythropoietin
Constitutively But Express Lactate Dehydrogenase in an
Oxygen-Dependent Manner
Taiho Kambe,
Junko Tada,
Mariko Chikuma,
Seiji Masuda,
Masaya Nagao,
Terumasa Tsuchiya,
Peter J. Ratcliffe, and
Ryuzo Sasaki
From the Division of Applied Life Sciences, Graduate School of
Agriculture, Kyoto University, Kyoto, Japan.
Embryonic stem cells and embryonal carcinoma P19 cells
produce erythropoietin (Epo) in an oxygen-independent manner, although lactate dehydrogenase A (LDHA) is hypoxia-inducible. To explore this
paradox, we studied the operation of cis-acting sequences from
these genes in P19 and Hep3B cells. The Epo gene promoter and 3
enhancer from P19 cells conveyed hypoxia-inducible responses in Hep3B
cells but not in P19 cells. Together with DNA sequencing and the normal
transcription start site of P19 Epo gene, this excluded the possibility
that the noninducibility of Epo gene in P19 cells was due to mutation
in these sequences or unusual initiation of transcription. In contrast,
reporter constructs containing LDHA enhancer and promoter were hypoxia
inducible in P19 and Hep3B cells, and mutation of a hypoxia- inducible
factor 1 (HIF-1) binding site abolished the hypoxic inducibility in
both cells, indicating that HIF-1 activation operates normally in P19 cells. Neither forced expression of hepatocyte nuclear factor 4 in P19
cells nor deletion of its binding site from the Epo enhancer was
effective in restoring Epo enhancer function. P19 cells may lack an
unidentified regulator(s) required for interaction of the Epo enhancer
with Epo and LDHA promoters.
Blood, Vol. 91 No. 4 (February 15), 1998:
pp. 1185-1195
© 1998 by The American Society of Hematology.
