PHOSPHORYLATION OF HISTONE H3 AT SERINE-10 IS CORRELATED WITH CHROMOSOME CONDENSATION DURING MITOSIS AND MEIOSIS IN TETRAHYMENA

H3 phosphorylation has been correlated with mitosis temporally in mamm alian cells and spatially in ciliated protozoa, In logarithmically gro wing Tetrahymena thermophila cells, for example, H3 phosphorylation ca n be detected in germline micronuclei that divide mitotically but not in somatic macronuclei that divide amitotically. Here, we demonstrate that micronuclear H3 phosphorylation occurs at a single site (Ser-10) in the amino-terminal domain of histone H3, the same site phosphorylat ed during mitosis in mammalian cells. Using an antibody specific for S er-10 phosphorylated H3, we show that, in Tetrahymena, this modificati on is correlated with mitotic and meiotic divisions of micronuclei in a fashion that closely coincides with chromosome condensation. Our dat a suggest that H3 phosphorylation at Ser-10 is a highly conserved even t among eukaryotes and is likely involved in both mitotic and meiotic chromosome condensation.