Objective: Histones bind in a sequence-independent manner to form chromatin. The aminoterminal tails of histones are targets for both phosphorylation and acetylation events. These modifi cations are thought to fundamentally regulate chromatin structure to accommodate transcription, DNA replication, mitosis and DNA repair. Regeneration of squamous epithelium is accompanied by marked cellular atypia, nuclear and nucleolar pleomorphism which could be confused with neoplasia. The aim of the study was to detect phosphorylated and acetylated forms of histone H3 in cytological smears. Design: Translational research. Setting: Department of Experimental Oncology, Masaryk Memorial Cancer Institute, Department of Pathological Physiology, Medical Faculty and Department of Obstetrics and Gynecology, Masaryk University, Czech Republic. Methods: Smears from women aged between 20 to 46 years were selected. The specimens comprised 10 squamous metaplasia, 20 CIN I, 12 CIN II, and 14 CIN III. The smears were stained with polyclonal antibodies against phosphorylated and acetylated forms of histone H3. Results: We found that nuclear positivity for phosphorylated (P) and acetylated (A) forms of histone H3 in CIN II (23% P, 33% A) and CIN III (25% P, 44% A) was higher in comparison with CIN I (8% P, 15% A) and metaplasia (11% P, 12% A). Conclusion: We revealed a marked association of histone H3 modifi cations with the progression of CIN II, CIN III in comparison with CIN I and metaplasia. Our results are in agreement with recent fi ndings: 1. staining of cells with anti-phospho-histone H3 antibodies therefore provides a highly specifi c marker for mitosis. 2. acetylation of nucleosomal histones correlates with localised transcriptional activity.

        Key words: histone H3, acetylation, phosphorylation, cervical intraepithelial neoplasia