Accumulation of BORIS upon S phase and mitosis arrest.

A) BORIS accumulates in differentiating keratinocytes of epidermis undergoing mitosis arrest as revealed by double labelling of human epidermis for BORIS (red) and Cyclin B (green); nuclear DNA (DAPI, blue). Scale bar: 15 µm. B) BORIS accumulates in primary keratinocytes treated for 24 h with inhibitors of the G1/S transition of the cell cycle (hydroxyurea, HU), the mitosis checkpoint (ZM77 for Aurora B kinase), or the genotoxic agent doxorubicin (DOXO). Microphotographs show merge of anti-BORIS, anti-γ-tubulin for centrosomes (green) and DAPI for nuclear DNA (blue). Scale bar: 10 µm. Arrows point at accumulation of BORIS. Note that DOXO provokes a generalised increased of BORIS. C) Relative BORIS mRNA as measured by RT-PCR, in primary keratinocytes treated as above. Representative of three independent experiments with cells from two different human individuals.