TRANSCRIPTION OF c-fos AND AP-1 BINDING ACTIVITY INCREASES UPON DIFFERENTIATION OF MOUSE F9
TERATOCARCINOMA CELLS
I. A. Tchuikin,1 M. S. Liangouzova, V. A. Pospelov
Institute of Cytology RAS, St. Petersburg, Russia;
1 e-mail: iliatchuikin@mail333.com
Retinoic acid (RA) causes differentiation of mouse F9 embryonic carcinoma cell line into primitive and parietal
(with dibutiril-cAMP) endoderm. The role of AP-1 transcription factor during RA-induced differentiation was studied in F9 cell line.
It was shown that differentiated cells acquired protein complexes, which are specifically bound to well characterized AP-1
32P-labeled binding sites from collagenase (Col-AP-1) and c-jun (Jun2-AP-l) promoters. These complexes contain
c-Fos/c-Jun with Col-AP-1 site and c-Jun/ATF-2 with Jun2-AP-l site as revealed by supershift analysis. DNA-binding activity of these
complexes is high in parietal endoderm but low-detectable in undifferentiatcd cells. DNA-binding activity of AP-1 transcription
factor correlates with increased expression of c-fos and c-jun genes. RT-PCR analysis showed an increase in
steady-state level of c-fos and c-jun gene transcription at the stage of parietal endoderm (terminally differentiated
F9 cells). Transcription of immediate early c-fos and c-jun genes and DNA-binding activity of c-Fos/c-Jun complex are
serum dependent. The rate of c-fos and c-jun gene transcription and DNA-binding activity of c-Fos/c-Jun complex
decreased in serum-starved cells, but was rapidly induced upon stimulation with serum. Undifferentiated F9 cells contain a very
low levl of c-fos mRNA, with may be a consequence of repressive chromatin structure in promoter region. Histone deacetylase
(HDAC) activity is necessary to restrict expression of specific number of genes, also HDAC inhibitors are well known inductors of
differentiation and anticancer agents. Frow cytometry analysis showed a decreased rate of proliferation of F9 cells after their
incubation with HDAC inhibitors, sodium butirate and trichostatin A. Also, these ihibitors induced the transcription of c-fos
gene. So, we conclude that HDAC activity may be necessary to sustain a high proliferative rate of Undifferentiated F9 cells.
Key words: F9 embryonic carcinoma cells, AP-1, differentiation, c-fos, HDAC
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