Abstract
We have analyzed the chromatin structure of the promoters of the c-FOS and U6 genes of mitotic HeLa cells, using dimethyl sulfate, ultraviolet light, and 4,5',8-trimethylpsoralen, as in vivo footprinting agents. The distribution of the damage induced by these agents was visualized by ligation-mediated PCR or terminal transferase-dependent PCR. We observed that transcription factors were displaced from their recognition sequences in these promoters during mitosis, and we found that the nucleosome positioning, which seems to potentiate transcription in these promoters during interphase, disappeared during mitosis. Thus, the complex nucleoprotein structures of these promoters were dissociated during mitosis, and this seems to contribute to the suppression of transcription in this phase of the cell cycle.
