and Mammalian Cells

suggesting that VP16 targets a conserved cellular function of HCF-1.) are viable but display reduced fertility. Loss of Ce HCF-1 protein at reduced temperatures (e.g., 12°C), however, leads to a high incidence of embryonic lethality and early embryonic mitotic and cytokinetic defects reminiscent of mammalian cell-division defects upon loss of HCF-1 function. Even when viable, however, at normal temperature, mutant embryos display reduced levels of phospho-histone H3 serine 10 (H3S10P), a modification implicated in both transcriptional and mitotic regulation. Mammalian cells with defective HCF-1 also display defects in mitotic H3S10P status.These results suggest that HCF-1 proteins possess conserved roles in the regulation of cell division and mitotic histone phosphorylation