Increased erythroid potentiating activity/tissue inhibitor of
metalloproteinases and jun/fos transcription factor complex characterize
tumor promoter-induced megakaryoblastic differentiation of K562 leukemia
cells
R Alitalo, J Partanen, L Pertovaara, E Holtta, L Sistonen, L Andersson and K Alitalo
Transplantation Laboratory, University of Helsinki, Finland.
Molecular cloning has revealed that erythroid potentiating activity (EPA)
and tissue inhibitor of metalloproteinases (TIMP) represent two distinct
activities of a single protein. We have studied the expression of the
EPA/TIMP gene at the mRNA and protein levels during 12-O-
tetradecanoyl-phorbol-13-acetate (TPA)-induced megakaryoblastic
differentiation of K562 human chronic myeloid leukemia cells. Northern
hybridization analysis showed that the EPA/TIMP mRNA was increased within 3
hours of TPA-induction and reached maximal levels (about 50- fold
induction) during the first day of treatment. The expression of mRNAs for
two major metalloproteinases, collagenase-I and stromelysin, were activated
in parallel in the differentiation-induced K562 cells. The increase of
EPA/TIMP mRNA correlated with increased EPA/TIMP protein biosynthesis and
secretion: the TPA-induced cells secreted substantially enhanced amounts of
metabolically labeled proteins, of which EPA/TIMP represented up to 50%
after the first day of treatment (over 100-fold induction). The induction
of EPA/TIMP mRNA was associated with its increased transcription. EPA/TIMP
induction required continuous protein synthesis, being completely inhibited
by addition of the protein synthesis inhibitor cycloheximide simultaneously
with TPA, but only partially inhibited in a time- dependent manner if
cycloheximide was added after TPA. Unlike in other cells tested, the jun
and c-fos transcription factor mRNAs showed a prolonged biphasic induction
response in K562 cells during TPA treatment. This response was associated
with enhanced activity of a transfected recombinant reporter plasmid
containing binding sites for the jun/fos transcription factor complex
(AP-1) similar to the TPA- responsive element (TRE) sequence we found in
the EPA/TIMP gene promoter. We suggest that the induction of EPA/TIMP and
several other genes specific for the differentiating K562 cells may be a
consequence of the sustained activation of immediate early genes encoding
transcription factors, such as jun and c-fos.
Volume 75,
Issue 10,
pp. 1974-1982,
05/15/1990
Copyright © 1990 by The American Society of Hematology
