A novel transcriptional regulatory factor that binds to the polyoma virus enhancer in a developmental stage-specific manner.

By using gel mobility shift assay, it was shown that the nuclear extract from F9 embryonal carcinoma (EC) cells contains a novel transcriptional regulatory factor, BF-H, that binds to the 5' upstream region of the early gene of polyoma virus. Two binding sites were located in the transcriptional enhancer domain "A" (nucleotide 5034-5041) and in the 5' upstream of the domain "A" (4998-5005), having a consensus motif (AAPuATGG) between them. Combination of in vitro mutagenesis with chloramphenicol acetyltransferase (CAT) assay revealed that BF-H is a positive transcriptional factor. Interestingly, the binding of BF-H disappeared after differentiation of F9 cells by treatment with retinoic acid, whereas BF-H was present in the F9 cells differentiated with both retinoic acid and dibutyryl cyclic AMP (dbcAMP). These observations suggest that BF-H regulates the expression of genes in a developmental stage-specific manner in early embryos of the mouse.