Chimeric liver transcription factors LFB1 (HNF1) containing the acidic activation domain of VP16 act as positive dominant interfering mutants.
The transcription factor LFB1 (HNF1) involved in the expression of liver-specific genes is characterized by a serine/threonine-rich activation domain whose transactivation potential differs between mammals and Xenopus. Exchanging the activation domain between the Xenopus and rat LFB1, we produced chimeric transactivators whose activities are primarily determined by the origin of the activation domain. By replacing the serine/threonine-rich activation domain of LFB1 with the acidic activation domain of VP16, we generated transcription factors that act as dominant positive interfering mutants on endogenous LFB1 in differentiated hepatoma cells. As these LFB1/VP16 chimeras show no self-squelching as observed with wild-type LFB1 and increase the activity of saturating LFB1, we postulate that acidic and serine/threonine-rich activation domains use different targets of the basal transcription machinery. Stable transfection of various LFB1 derivatives, including those containing the VP16 transactivation domain, into the dedifferentiated C2 hepatoma cell resulted in cell clones stably expressing LFB1 function. However, as in none of these clones the chromosomal albumin genes are activated, we conclude that the presence of functional LFB1 may not be sufficient to reactivate liver-specific functions lost in dedifferentiated hepatoma cells.
Denecke
B
B
Institut für Zellbiologie (Tumorforschung), Universität-Gesamthochschule-Essen, Germany.
Bartkowski
S
S
Senkel
S
S
Klein-Hitpass
L
L
Ryffel
G U
GU
D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D017124:Conserved Sequence; D003587:Cytomegalovirus / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005822:Genetic Vectors; D051537:Hepatocyte Nuclear Factor 1; D051538:Hepatocyte Nuclear Factor 1-alpha; D051539:Hepatocyte Nuclear Factor 1-beta; D017405:Herpes Simplex Virus Protein Vmw65 / Q000235:genetics / Q000378:metabolism*; D008099:Liver / Q000378:metabolism*; D008114:Liver Neoplasms, Experimental / Q000378:metabolism; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009687:Nuclear Proteins; D011401:Promoter Regions, Genetic; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000378:metabolism*; D015183:Restriction Mapping; D016385:TATA Box; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation; D014162:Transfection; D014981:Xenopus; D029867:Xenopus Proteins
D004268:DNA-Binding Proteins; D051538:Hepatocyte Nuclear Factor 1-alpha; D017405:Herpes Simplex Virus Protein Vmw65; C496489:Hnf1a protein, rat; C000627649:Hnf1b protein, Xenopus; D009687:Nuclear Proteins; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; D029867:Xenopus Proteins; C496490:hnf1a protein, Xenopus; D051537:Hepatocyte Nuclear Factor 1; D051539:Hepatocyte Nuclear Factor 1-beta