Altered DNA/protein complexes specific for the beta-interferon regulatory region observed in murine embryonal carcinoma F9 cells.

Abstract

Murine embryonal carcinoma (EC) F9 cells do not produce interferon (IFN) at the protein or RNA level in response to inducing agents, while retinoic acid differentiated F9 cells do produce IFN. A probe was constructed spanning positions -104 to -39 of the human beta-IFN upstream regulatory region to examine this developmental control at the level of a transcriptional regulatory mechanism. Gel mobility shift analyses were used to examine this molecular mechanism to determine whether the differential expression of positive or negative trans-acting factors may act to control beta-IFN expression in undifferentiated EC cells. These analyses showed that while nuclear extracts from poly-I,C induced L929 cells, in the IFN producing cell line, showed two shifted bands, nuclear extracts from both induced and uninduced F9 cells showed only one shifted band using the -104/-39 probe. While this single shifted band co-migrated with the faster migrating species of L929 cell extracts, competition analysis revealed differences between the two complexes. An oligonucleotide representing the positive regulatory domain PRDII competed efficiently for the probe when induced F9 cell extracts were examined, but failed to compete when induced L929 cell extracts were examined. In contrast, an oligonucleotide representing the positive regulatory domain PRDI competed very well when induced L929 cell extracts were examined but had only a minimal effect when induced F9 cell extracts were examined. These data suggest the involvement of developmentally regulated transcriptional factor(s) which have yet to be characterized.