Abstract: This invention relates to a method of constructing a villin gene hybrid by inserting an I-Sce I restriction site next to or within a gene or cDNA encoding a villin protein. The insertion site of the I-Sce I restriction site is chosen as to provide a first downstream part and a second upstream part from the site, containing at least twelve nucleotides of the gene or cDNA encoding the villin protein. Furthermore, the insertion of the restriction permits a high frequency of homologous recombination events. The villin gene hybrid may be used to transfect eukaryotic cells, and particularly, embryonic stem cells.

Abstract: The Far Upstream Element (FUSE) of the human c-myc gene stimulates expression in undifferentiated cells. A FUSE binding protein (FBP), also referred to as DROME (DNA-binding regulator of c-myc expression), is active in undifferentiated but not differentiated cell extracts. Cloned FBP exhibits the same DNA-binding specificity as the purified human protein and can trans-activate in a FUSE dependent manner. Sequence-specific binding to the FUSE oligonucleotide requires at least two copies of a repeat-helix unit which defines a new DNA-binding motif. Expression of FBP mRNA declined in parallel with decreased FUSE binding activity upon differentiation suggesting transcriptional regulation of FBP.