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Mol. Cell. Biol., 11 1997, 6311-6320, Vol 17, No. 11
D Chaya, C Fougere-Deschatrette and MC Weiss
Among the liver-enriched transcription factors identified to date, only
expression of hepatocyte nuclear factor 4 (HNF4) and hepatocyte nuclear
factor 1 (HNF1) is in strict correlation with hepatic differentiation in
cultured rat hepatoma cells. Indeed, differentiated hepatoma cells that
stably express an extensive set of adult hepatic functions express
liver-enriched transcription factors, while dedifferentiated cells that
have lost expression of all these hepatic functions no longer express HNF4
and HNF1. We describe a new heritable phenotype, designated as uncoupled,
in which there is a spontaneous dissociation between the expression of
these transcription factors and that of the hepatic functions. Cells
presenting this phenotype, isolated from differentiated hepatoma cells,
cease to accumulate all transcripts coding for hepatic functions but
nevertheless maintain expression of HNF4 and HNF1. Transitory transfection
experiments indicate that these two factors present in these cells have
transcriptional activity similar to that of differentiated hepatoma cells.
Characterization of the appropriate intertypic cell hybrids demonstrates
that this new phenotype is recessive to the dedifferentiated state and
fails to be complemented by differentiated cells. These results indicate
the existence of mechanisms that inhibit transcription of genes coding for
hepatocyte functions in spite of the presence of functional HNF4 and HNF1.
Cells of the uncoupled phenotype present certain properties of oval cells
described for pathological states of the liver.
Copyright © 1997, American Society for Microbiology
Liver-enriched transcription factors uncoupled from expression of hepatic functions in hepatoma cell lines
UMR 0321 du CNRS, Departement de Biologie Moleculaire, Institut Pasteur, Paris, France.
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