H3K4me3 - dependent epigenetic memory regulates transcriptional reactivation in the oocyte

SELECTED ORAL COMMUNICATIONS, SESSION 52: EPIGENETIC PATTERN IN OOCYTE AND EMBRYO, Tuesday 16 June 2015. This article/study appears in: Abstract book of the 31st ESHRE Annual Meeting, Lisbon, Portugal, 14-17 June 2015.Study question: How does the oocyte regulate its transcriptional activity in light of its prolonged meiotic arrest? Summary answer: A histone methylation-mediated epigenetic memory programed by the demethylase KDM5 is required for the correct temporal reactivation of the oocyte's transcriptional activity. What is known already: During oogenesis oocytes transit from stages of transcriptional activity to those of transcriptional quiescence, and such transitions are believed to be essential for proper gamete formation. Although the temporal regulation of these transitions has been well documented across diverse organisms, the molecular mechanisms underlying these processes remain largely unknown.Funding by national/international organization(s) – Partly funded by Fundação para a Ciência e a Tecnologia

Fission Yeast Rad26 Is a Regulatory Subunit of the Rad3 Checkpoint Kinase

Fission yeast Rad3 is a member of a family of phosphoinositide 3-kinase -related kinases required for the maintenance of genomic stability in all eukaryotic cells. In fission yeast, Rad3 regulates the cell cycle arrest and recovery activities associated with the G2/M checkpoint. We have developed an assay that directly measures Rad3 kinase activity in cells expressing physiological levels of the protein. Using the assay, we demonstrate directly that Rad3 kinase activity is stimulated by checkpoint signals. Of the five other G2/M checkpoint proteins (Hus1, Rad1, Rad9, Rad17, and Rad26), only Rad26 was required for Rad3 kinase activity. Because Rad26 has previously been shown to interact constitutively with Rad3, our results demonstrate that Rad26 is a regulatory subunit, and Rad3 is the catalytic subunit, of the Rad3/Rad26 kinase complex. Analysis of Rad26/Rad3 kinase activation in rad26.T12, a mutant that is proficient for cell cycle arrest, but defective in recovery, suggests that these two responses to checkpoint signals require quantitatively different levels of kinase activity from the Rad3/Rad26 complex