Fig. 3. The cyclin B1 promoter interacts with transcription factors during mitosis in vivo. Genomic footprinting of the non-coding strand of the human cyclin B1 promoter from asynchronous (Async.) and MSO HeLa cells (lanes 2 and 3), and of the coding strand of the human hsp70 promoter from MSO HeLa cells (lane 5). As a control, the DMS reactivity for DNA purified from asynchronous HeLa cells is shown (In vitro). The changes in DMS reactivity found in asynchronous and MSO cells are noted at the corresponding G residues by an asterisk (hypersensitivity) and by underlines (protection).