Deposition of Acetylated Histones by RNAP II Promoter Clearance May Occur at Onset of Zygotic Gene Activation in Preimplantation Mouse Embryos

Mikiko TOKORO, Seung-Wook SHIN, Satoshi NISHIKAWA, Hyang-Heun LEE, Yuki HATANAKA, Tomoko AMANO, Tasuku MITANI, Hiromi KATO, Masayuki ANZAI, Satoshi KISHIGAMI, Kazuhiro SAEKI, Yoshihiko HOSOI (+2 others)
2010 Journal of reproduction and development  
We investigated the contribution of phosphorylated RNA polymerase II (RNAP II) and dynamic epigenetic changes to the onset of minor zygotic gene activation (ZGA). Using immunofluorescence staining, we observed that the nuclear localization of RNAP II was initiated by 6 hours post insemination (hpi), whereas RNAP II phosphorylated at serine residue 5 of the carboxyl-terminal domain (CTD) was localized by 9 hpi, and then RNAP II phosphorylated at serine residue 2 of the CTD was localized in the
more » ... cleus of embryos by 12 hpi. In a transient gene expression assay using a plasmid reporter gene (pβ-actin/luciferase+/SV40) injected during 6-9 hpi into the male pronucleus, the luciferase+ gene was actively transcribed and translated by 13 and 15 hpi, respectively, indicating that a transcriptionally silent state persisted for at least 4 hours after injection. We found that the methylation status in the chicken β-actin promoter region of the plasmid reporter gene may not be associated with the transcriptionally silent state before minor ZGA. Exposure to trichostatin A did not induce premature expression of the silent reporter gene injected into 1-cell embryos containing histone deacetylase activity and did not affect the amount of luciferase produced per embryo. Acetylated histone H3 lysine 9/14 and acetylated histone H4 lysine 12 and 16 were enriched preferentially in the injected reporter gene at least until 13 hpi, which coincided with the transcriptionally active state. Taken together, these results suggest that deposition of selectively acetylated histones onto the chromatin of 1-cell embryos functions together with transcriptional elongation by RNAP II and that this sequential chromatin remodeling is involved in the molecular mechanism associated with the onset of minor ZGA in the preimplantation mouse embryo.
doi:10.1262/jrd.10-088m pmid:20710121 fatcat:qyvz6nhjsfc27fewtto6oc3vkq