Quantitative in Vivo Analysis of Chromatin Binding of Polycomb and Trithorax Group Proteins Reveals Retention of ASH1 on Mitotic Chromatin Philipp A
Published online 10 April 2013 Nucleic Acids Research, 2013, Vol. 41, No. 10 5235–5250 doi:10.1093/nar/gkt217 Quantitative in vivo analysis of chromatin binding of Polycomb and Trithorax group proteins reveals retention of ASH1 on mitotic chromatin Philipp A. Steffen1, Joa˜ o Pedro Fonseca1, Cornelia Ga¨ nger1, Eva Dworschak1, Tobias Kockmann2, Christian Beisel2 and Leonie Ringrose1,* 1Institute of Molecular Biotechnology (IMBA), Dr. Bohr-Gasse 3, 1030 Vienna, Austria and 2Department of Biosystems Science and Engineering, ETH Zu¨ rich, Mattenstrasse 26, 4058 Basel, Switzerland Received November 8, 2012; Revised February 15, 2013; Accepted March 8, 2013 ABSTRACT of their targets (6). For several target genes, reporter assays have shown that the PcG and TrxG can maintain Downloaded from The Polycomb (PcG) and Trithorax (TrxG) group mitotically heritable stable states of both silent (7,8) and proteins work antagonistically on several hundred activated gene expression (9–11) depending on the initial developmentally important target genes, giving transcriptional status of the target gene. Thus, these stable mitotic memory, but also allowing flexibility proteins have the capacity to maintain stable epigenetic of gene expression states. How this is achieved in memory of transcriptional decisions, in the absence of http://nar.oxfordjournals.org/ quantitative terms is poorly understood. Here, we the initial determining transcription factors. However, present a quantitative kinetic analysis in living this regulatory system also has an inherent flexibility, Drosophila of the PcG proteins Enhancer of Zeste, allowing PcG and TrxG target genes to switch their tran- (E(Z)), Pleiohomeotic (PHO) and Polycomb (PC) and scriptional status dynamically on developmental or experi- the TrxG protein absent, small or homeotic discs 1 mental cues (9,12).
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