Histone H2A.F/Z mRNA is stored in the egg cytoplasm and basally regulated in the sea urchin embryo.

The sea urchin H2A.F/Z histone is a member of a subclass of highly conserved H2A variants. Sequence analysis confirms that H2A.F/Z mRNA is polyadenylated. In situ hybridization studies demonstrate that maternal H2A.F/Z message is stored in the egg cytoplasm and present at equal levels in all cells of the mesenchyme blastula-stage embryo, suggesting that H2A.F/Z is not coordinately regulated with DNA synthesis. When blastula-stage embryos were exposed to DNA synthesis inhibitors, no effect on the steady-state level of H2A.F/Z mRNA was observed, while the level of late class H2B mRNA decreased substantially. These results provide evidence that the basal mode of regulation of this unusual histone variant is conserved evolutionarily.