Past exam of the biochemistry and Molecular Biology course of the University of Cambridge / 2025 / Paper 2 / Section C / 14 / m

The extract forms a slower-migrating labelled complex. Addition of either anti-TCF transcription factor or anti-HNF1β replaces much of the lower shifted band with an even slower species. The results support participation of both TCF transcription factor and HNF1β in promoter-associated complexes, assuming the antibodies are specific. The separate supershifts are consistent with their presence together, but cannot exclude two unresolved, similarly migrating complexes containing one factor each. They do not by themselves establish direct binding of each factor to its own predicted motif, physical interaction between the factors, or occupation of the native promoter in intact biological cells. Mutant binding sites, purified components and a chromatin-occupancy assay address those distinct claims.